| 0/0 |
2026/08/12 13:19 |
flow |
repro-c |
10m
Results: map[EquivalenceAnalysis:The reproducer successfully triggered the target bug. The crash report shows `[ BUG: Invalid wait context ]` with the exact same stack trace as the original report: `xen_timer_callback` -> `kvm_xen_set_evtchn_fast` -> lock acquisition. The original report was on a PREEMPT_RT kernel, which additionally triggered a "sleeping function called from invalid context" warning because spinlocks/rwlocks sleep in RT, but the underlying issue (taking `gpc->lock` in hardirq context from the hrtimer callback) is identical and caught by lockdep's wait context checks in both cases. OtherCrashReports:<nil> ReproC:#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
#define KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL ((uint32_t)(-1))
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
#define MY_KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
int main(void)
{
int kvm_fd, vm_fd, vcpu_fd;
struct my_kvm_xen_vcpu_attr attr;
int res;
kvm_fd = open("/dev/kvm", O_RDWR);
if (kvm_fd < 0) {
printf("[-] Failed to open /dev/kvm: %s\n", strerror(errno));
exit(1);
}
printf("[+] open /dev/kvm successful.\n");
vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0);
if (vm_fd < 0) {
printf("[-] Failed to KVM_CREATE_VM: %s\n", strerror(errno));
exit(1);
}
printf("[+] KVM_CREATE_VM successful.\n");
vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);
if (vcpu_fd < 0) {
printf("[-] Failed to KVM_CREATE_VCPU: %s\n", strerror(errno));
exit(1);
}
printf("[+] KVM_CREATE_VCPU successful.\n");
memset(&attr, 0, sizeof(attr));
attr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
attr.u.timer.port = 1;
attr.u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
attr.u.timer.expires_ns = 1000000000ULL;
res = ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr);
if (res < 0) {
printf("[-] Failed to MY_KVM_XEN_VCPU_SET_ATTR: %s\n", strerror(errno));
exit(1);
}
printf("[+] MY_KVM_XEN_VCPU_SET_ATTR successful.\n");
printf("[+] Waiting for timer to fire...\n");
sleep(2);
close(vcpu_fd);
close(vm_fd);
close(kvm_fd);
printf("[+] Done.\n");
return 0;
}
Reproduced:true ReproducedBugTitle:WARNING: locking bug in kvm_xen_set_evtchn_fast ReproducedCrashReport:=============================
[ BUG: Invalid wait context ]
syzkaller #1 Not tainted
-----------------------------
swapper/0/0 is trying to lock:
ffff88810d699bb0 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x9a0 arch/x86/kvm/xen.c:1829
other info that might help us debug this:
context-{2:2}
locks held by swapper/0/0: 1, last CPU#0:
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1bc/0x9a0 arch/x86/kvm/xen.c:1827
stack backtrace:
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #1 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_lock_invalid_wait_context kernel/locking/lockdep.c:4846 [inline]
check_wait_context kernel/locking/lockdep.c:4918 [inline]
__lock_acquire+0xef0/0x2e50 kernel/locking/lockdep.c:5204
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5906
__raw_read_lock_irqsave include/linux/rwlock_api_smp.h:174 [inline]
_raw_read_lock_irqsave+0x48/0x60 kernel/locking/spinlock.c:240
kvm_xen_set_evtchn_fast+0x1f4/0x9a0 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x371/0xa10 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x448/0x910 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64
Code: 8d 8f 02 e9 d3 03 03 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d b3 65 15 00 fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
RSP: 0018:ffffffff8e807ca0 EFLAGS: 00000246
RAX: 00000000001183f3 RBX: ffffffff819a214c RCX: 0000000080000001
RDX: 0000000000000001 RSI: ffffffff8e176c40 RDI: ffffffff8c326480
RBP: ffffffff8e807d78 R08: ffff8881386338db R09: 1ffff110270c671b
R10: dffffc0000000000 R11: ffffed10270c671c R12: 0000000000000000
R13: 1ffffffff1d11e20 R14: 1ffffffff1d00f9c R15: dffffc0000000000
arch_safe_halt arch/x86/kernel/process.c:767 [inline]
default_idle+0x9/0x20 arch/x86/kernel/process.c:768
default_idle_call+0x72/0xb0 kernel/sched/idle.c:122
cpuidle_idle_call kernel/sched/idle.c:199 [inline]
do_idle+0x1cc/0x540 kernel/sched/idle.c:355
cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:454
rest_init+0x378/0x3a0 init/main.c:727
start_kernel+0x392/0x3e0 init/main.c:1185
x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291
common_startup_64+0x13e/0x157
</TASK>
----------------
Code disassembly (best guess):
0: 8d 8f 02 e9 d3 03 lea 0x3d3e902(%rdi),%ecx
6: 03 00 add (%rax),%eax
8: cc int3
9: cc int3
a: cc int3
b: 90 nop
c: 90 nop
d: 90 nop
e: 90 nop
f: 90 nop
10: 90 nop
11: 90 nop
12: 90 nop
13: 90 nop
14: 90 nop
15: 90 nop
16: 90 nop
17: 90 nop
18: 90 nop
19: 90 nop
1a: 90 nop
1b: f3 0f 1e fa endbr64
1f: 66 90 xchg %ax,%ax
21: 0f 00 2d b3 65 15 00 verw 0x1565b3(%rip) # 0x1565db
28: fb sti
29: f4 hlt
* 2a: c3 ret <-- trapping instruction
2b: cc int3
2c: cc int3
2d: cc int3
2e: cc int3
2f: cc int3
30: cc int3
31: cc int3
32: cc int3
33: cc int3
34: cc int3
35: cc int3
36: cc int3
37: cc int3
38: cc int3
39: cc int3
3a: cc int3
3b: 90 nop
3c: 90 nop
3d: 90 nop
3e: 90 nop
3f: 90 nop
]
|
| 1/1 |
2026/08/12 13:19 |
action |
kernel-checkouter |
0m
Results: map[KernelSrc:/app/workdir/cache/src/26766716579cdcff13b5e3416aa2d1ff891e8337]
|
| 2/1 |
2026/08/12 13:19 |
action |
kernel-builder |
0m
Results: map[KernelObj:/app/workdir/cache/build/3c9f8cd174126c09e995d94ae9cc5aacc87d5c60]
|
| 3/1 |
2026/08/12 13:19 |
action |
codesearch-prepare |
0m
Results: map[Index:codesearch-index]
|
| 4/1 |
2026/08/12 13:19 |
agent |
initial-researcher |
0m
Model:
Instruction: You are a security researcher with deep Linux kernel background.
Your goal is to analyze a Linux kernel bug description and propose a strategy to reproduce it
with a minimal, standalone C program for the strictly defensive purpose of verifying a bugfix.
=== TOOL SELECTION GUIDELINES ===
- When looking up C function or struct definitions, prefer codesearch-definition-source
and codesearch-struct-layout first.
- Fall back to read-file or grepper only if symbol lookup fails or when inspecting macros,
headers, or non-C files.
=== CRITICAL PROHIBITIONS ===
- Do NOT propose an exploit. Focus solely on minimal technical reproduction of the bug state.
- Do NOT write long explanations. Keep your analysis and strategy proposal concise.
- Do NOT assume that the target bug has already been fixed just because a git commit title
or description mentions a similar bug or fix. Commit messages often reference related issues
or partial fixes. Proceed with proposing a reproduction strategy regardless of historical fix commits.
Prefer calling several tools at the same time to save round-trips.
Prompt: Bug Description: BUG: sleeping function called from invalid context in kvm_xen_set_evtchn_fast
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:248
in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 5622, name: syz-executor363
preempt_count: 10000, expected: 0
RCU nest depth: 1, expected: 1
locks held by syz-executor363/5622: 4, last CPU#0:
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: __simple_recursive_removal+0x19a/0x520 fs/libfs.c:619
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
#2: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rtlock_slowlock_locked+0x2ab/0x3c20 kernel/locking/rtmutex.c:1874
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1be/0x990 arch/x86/kvm/xen.c:1827
irq event stamp: 13272
hardirqs last enabled at (13271): [<ffffffff8b53b4b3>] __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:187 [inline]
hardirqs last enabled at (13271): [<ffffffff8b53b4b3>] _raw_spin_unlock_irq+0x23/0x50 kernel/locking/spinlock.c:206
hardirqs last disabled at (13272): [<ffffffff8b501aee>] sysvec_apic_timer_interrupt+0xe/0xc0 arch/x86/kernel/apic/apic.c:1062
softirqs last enabled at (6940): [<ffffffff81882fe0>] __local_bh_enable_ip+0x1a0/0x2b0 kernel/softirq.c:305
softirqs last disabled at (6932): [<ffffffff891cda09>] local_bh_disable include/linux/bottom_half.h:20 [inline]
softirqs last disabled at (6932): [<ffffffff891cda09>] __alloc_skb+0x189/0x7a0 net/core/skbuff.c:697
Preemption disabled at:
[<ffffffff81883b8e>] irq_enter_rcu+0x1e/0x1f0 kernel/softirq.c:668
CPU: 0 UID: 0 PID: 5622 Comm: syz-executor363 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
__might_resched+0x329/0x480 kernel/sched/core.c:9194
rt_read_lock+0xa9/0x4b0 kernel/locking/spinlock_rt.c:248
kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x3a0/0xaf0 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x44a/0x900 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:rt_mutex_owner include/linux/rtmutex.h:52 [inline]
RIP: 0010:rtmutex_spin_on_owner kernel/locking/rtmutex.c:1504 [inline]
RIP: 0010:rtlock_slowlock_locked+0x34e5/0x3c20 kernel/locking/rtmutex.c:1893
Code: 80 3c 01 00 4c 8b b4 24 80 00 00 00 4c 8b 2c 24 74 08 4c 89 ef e8 db 0e df f6 48 8d 84 24 60 01 00 00 49 39 45 00 75 6c f3 90 <48> b8 00 00 00 00 00 fc ff df 48 8b 8c 24 a8 00 00 00 80 3c 01 00
RSP: 0018:ffffc90004e6f7a0 EFLAGS: 00000246
RAX: ffffc90004e6f900 RBX: 1ffff11006ff9bbe RCX: 1ffffffff1ca7871
RDX: 00000000e6b90d15 RSI: ffffffff8bcbd060 RDI: 0000000000000001
RBP: ffffc90004e6f9f0 R08: 1d00000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8e3c3880 R12: ffff888037fcddc0
R13: ffffffff8e53c388 R14: ffffffff8e53c390 R15: 1ffff11006ff9bba
rtlock_slowlock kernel/locking/rtmutex.c:1922 [inline]
rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
__rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
rt_spin_lock+0x165/0x400 kernel/locking/spinlock_rt.c:57
spin_lock include/linux/spinlock_rt.h:45 [inline]
simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
__simple_recursive_removal+0x215/0x520 fs/libfs.c:623
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:781
kvm_destroy_vm_debugfs virt/kvm/kvm_main.c:988 [inline]
kvm_destroy_vm virt/kvm/kvm_main.c:1261 [inline]
kvm_put_kvm+0x147/0xae0 virt/kvm/kvm_main.c:1331
kvm_vm_release+0x46/0x50 virt/kvm/kvm_main.c:1354
__fput+0x42a/0xa80 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x73a/0x2360 kernel/exit.c:1009
do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
__do_sys_exit_group kernel/exit.c:1163 [inline]
__se_sys_exit_group kernel/exit.c:1161 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1161
x64_sys_call+0x18bf/0x18c0 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f132ec60d05
Code: Unable to access opcode bytes at 0x7f132ec60cdb.
RSP: 002b:00007ffe413e3968 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f132ec60d05
RDX: 00000000000000e7 RSI: ffffffffffffffd8 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000009 R11: 0000000000000202 R12: 0000000000000000
R13: 00007f132ecfa118 R14: 00007f132ecfc3c8 R15: 00007f132ecfc3e0
</TASK>
=============================
[ BUG: Invalid wait context ]
syzkaller #0 Tainted: G W
-----------------------------
syz-executor363/5622 is trying to lock:
ffff888038241530 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
other info that might help us debug this:
context-{2:2}
locks held by syz-executor363/5622: 4, last CPU#0:
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: __simple_recursive_removal+0x19a/0x520 fs/libfs.c:619
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
#2: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rtlock_slowlock_locked+0x2ab/0x3c20 kernel/locking/rtmutex.c:1874
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1be/0x990 arch/x86/kvm/xen.c:1827
stack backtrace:
CPU: 0 UID: 0 PID: 5622 Comm: syz-executor363 Tainted: G W syzkaller #0 PREEMPT_{RT,(full)}
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_lock_invalid_wait_context kernel/locking/lockdep.c:4846 [inline]
check_wait_context kernel/locking/lockdep.c:4918 [inline]
__lock_acquire+0xef0/0x2e40 kernel/locking/lockdep.c:5204
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5906
rt_read_lock+0xcc/0x4b0 kernel/locking/spinlock_rt.c:249
kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x3a0/0xaf0 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x44a/0x900 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:rt_mutex_owner include/linux/rtmutex.h:52 [inline]
RIP: 0010:rtmutex_spin_on_owner kernel/locking/rtmutex.c:1504 [inline]
RIP: 0010:rtlock_slowlock_locked+0x34e5/0x3c20 kernel/locking/rtmutex.c:1893
Code: 80 3c 01 00 4c 8b b4 24 80 00 00 00 4c 8b 2c 24 74 08 4c 89 ef e8 db 0e df f6 48 8d 84 24 60 01 00 00 49 39 45 00 75 6c f3 90 <48> b8 00 00 00 00 00 fc ff df 48 8b 8c 24 a8 00 00 00 80 3c 01 00
RSP: 0018:ffffc90004e6f7a0 EFLAGS: 00000246
RAX: ffffc90004e6f900 RBX: 1ffff11006ff9bbe RCX: 1ffffffff1ca7871
RDX: 00000000e6b90d15 RSI: ffffffff8bcbd060 RDI: 0000000000000001
RBP: ffffc90004e6f9f0 R08: 1d00000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8e3c3880 R12: ffff888037fcddc0
R13: ffffffff8e53c388 R14: ffffffff8e53c390 R15: 1ffff11006ff9bba
rtlock_slowlock kernel/locking/rtmutex.c:1922 [inline]
rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
__rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
rt_spin_lock+0x165/0x400 kernel/locking/spinlock_rt.c:57
spin_lock include/linux/spinlock_rt.h:45 [inline]
simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
__simple_recursive_removal+0x215/0x520 fs/libfs.c:623
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:781
kvm_destroy_vm_debugfs virt/kvm/kvm_main.c:988 [inline]
kvm_destroy_vm virt/kvm/kvm_main.c:1261 [inline]
kvm_put_kvm+0x147/0xae0 virt/kvm/kvm_main.c:1331
kvm_vm_release+0x46/0x50 virt/kvm/kvm_main.c:1354
__fput+0x42a/0xa80 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x73a/0x2360 kernel/exit.c:1009
do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
__do_sys_exit_group kernel/exit.c:1163 [inline]
__se_sys_exit_group kernel/exit.c:1161 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1161
x64_sys_call+0x18bf/0x18c0 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f132ec60d05
Code: Unable to access opcode bytes at 0x7f132ec60cdb.
RSP: 002b:00007ffe413e3968 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f132ec60d05
RDX: 00000000000000e7 RSI: ffffffffffffffd8 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000009 R11: 0000000000000202 R12: 0000000000000000
R13: 00007f132ecfa118 R14: 00007f132ecfc3c8 R15: 00007f132ecfc3e0
</TASK>
----------------
Code disassembly (best guess):
0: 80 3c 01 00 cmpb $0x0,(%rcx,%rax,1)
4: 4c 8b b4 24 80 00 00 mov 0x80(%rsp),%r14
b: 00
c: 4c 8b 2c 24 mov (%rsp),%r13
10: 74 08 je 0x1a
12: 4c 89 ef mov %r13,%rdi
15: e8 db 0e df f6 call 0xf6df0ef5
1a: 48 8d 84 24 60 01 00 lea 0x160(%rsp),%rax
21: 00
22: 49 39 45 00 cmp %rax,0x0(%r13)
26: 75 6c jne 0x94
28: f3 90 pause
* 2a: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax <-- trapping instruction
31: fc ff df
34: 48 8b 8c 24 a8 00 00 mov 0xa8(%rsp),%rcx
3b: 00
3c: 80 3c 01 00 cmpb $0x0,(%rcx,%rax,1)
Reply: An analysis of the bug report reveals that this is a PREEMPT_RT specific issue in the KVM Xen emulation code.
### Bug Analysis
1. **Context**: The bug is a "sleeping function called from invalid context" which occurs in a kernel compiled with `CONFIG_PREEMPT_RT`.
2. **Trigger**: The stack trace shows that the high-resolution timer callback `xen_timer_callback()` executes in hardirq context (as it is armed with `HRTIMER_MODE_ABS_HARD`).
3. **Root Cause**: `xen_timer_callback()` calls `kvm_xen_set_evtchn_fast()`, which unconditionally attempts to acquire a read lock on `gpc->lock` (a `rwlock_t`) via `read_lock_irqsave()`. In PREEMPT_RT kernels, `rwlock_t` is mapped to a sleeping lock (`rt_read_lock`). Acquiring a sleeping lock in hardirq context is invalid and triggers the BUG.
4. **Path to Reproduce**: We can trigger this by simply creating a KVM VM and VCPU, and then using the `KVM_XEN_VCPU_SET_ATTR` ioctl to arm the Xen timer (`KVM_XEN_VCPU_ATTR_TYPE_TIMER`). If we set the timer expiration to a short time in the future, `kvm_xen_start_timer()` will arm the hrtimer asynchronously. When the timer expires, it fires in hardirq context and hits the invalid lock acquisition.
### Reproduction Strategy
We can reproduce this issue with a minimal C program that:
1. Opens `/dev/kvm` and creates a VM and a VCPU.
2. Calls the `KVM_XEN_VCPU_SET_ATTR` ioctl on the VCPU to set up a Xen timer.
3. Sets the timer's `expires_ns` to a value safely in the future (e.g., 1 second) to ensure the timer is armed asynchronously rather than firing synchronously during the ioctl.
4. Sleeps to allow the timer to expire and trigger the bug in the interrupt context.
### Minimal C Reproducer
```c
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
/* Define KVM Xen constants in case they are missing from older headers */
#ifndef KVM_XEN_VCPU_ATTR_TYPE_TIMER
#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
#endif
#ifndef KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL
#define KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL ((uint32_t)(-1))
#endif
/* Local definition of the attribute struct to ensure compilation */
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
#define MY_KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
int main(void)
{
int kvm_fd, vm_fd, vcpu_fd;
struct my_kvm_xen_vcpu_attr attr = {0};
kvm_fd = open("/dev/kvm", O_RDWR);
if (kvm_fd < 0) {
perror("open /dev/kvm");
return 1;
}
vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0);
if (vm_fd < 0) {
perror("KVM_CREATE_VM");
return 1;
}
vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);
if (vcpu_fd < 0) {
perror("KVM_CREATE_VCPU");
return 1;
}
/*
* Arm the Xen timer.
* The guest kvmclock starts at 0 when the VM is created.
* Setting expires_ns to 1 second ensures delta > 0, forcing
* the hrtimer to be armed asynchronously.
*/
attr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
attr.u.timer.port = 1;
attr.u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
attr.u.timer.expires_ns = 1000000000ULL; /* 1 second */
if (ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr) < 0) {
perror("KVM_XEN_VCPU_SET_ATTR");
return 1;
}
/* Wait for the hrtimer to fire in hardirq context */
sleep(2);
return 0;
}
```
|
| 5/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 8821
output: 41
thoughts: 724
Thoughts: **My Thought Process Regarding the KVM Xen Event Channel Bug**
Right, I've just encountered a bug report that looks quite interesting, specifically related to KVM and Xen integration within a PREEMPT_RT kernel. The core of the issue is flagged as "BUG: sleeping function called from invalid context in kvm_xen_set_evtchn_fast." This immediately tells me we're dealing with a situation where a function designed to potentially sleep (meaning it might block and yield the CPU) is being invoked in a context where that's absolutely forbidden – the most likely culprit being a hard interrupt context. The fact that it's occurring in a `PREEMPT_RT` kernel (`PREEMPT_{RT,(full)}`) is a critical clue, as this kernel variant enforces stricter rules about preemption and sleeping locks.
Looking at the call trace provided, it paints a clear picture of the execution path leading to the failure:
* The execution originates within an interrupt handler (`<IRQ>`).
* It proceeds through standard kernel debugging and scheduling functions like `dump_stack_lvl` and `__might_resched`.
* Crucially, it then hits `rt_read_lock`. This is where my alarm bells start ringing. In the context of a PREEMPT_RT kernel, `rt_read_lock` is not just a spinlock; it's a *sleeping* read-write lock.
* Following that, we see the problematic function itself, `kvm_xen_set_evtchn_fast`, being called.
* The trace indicates that `kvm_xen_set_evtchn_fast` is being invoked by `xen_timer_callback`.
* The path continues up through the high-resolution timer (hrtimer) infrastructure: `__run_hrtimer`, `__hrtimer_run_queues`, `hrtimer_interrupt`.
* And finally, the interrupt handler that eventually triggered all of this appears to be the local APIC timer interrupt (`local_apic_timer_interrupt`, `__sysvec_apic_timer_interrupt`, `sysvec_apic_timer_interrupt`).
So, the sequence is: APIC timer interrupt fires, which triggers an hrtimer callback (`xen_timer_callback`), which in turn calls `kvm_xen_set_evtchn_fast`. The key insight here is that `xen_timer_callback` is, by definition, an hrtimer callback. Now, hrtimers in PREEMPT_RT can behave in a couple of ways. They *can* be configured to run in a hardirq context if they are explicitly marked with something like `HRTIMER_MODE_HARD`. Alternatively, even a "regular" hrtimer might end up executing its callback in a hardirq context if the timer was set up to expire during an interrupt or if the interrupt handler itself dispatches it this way.
The critical juncture, as I noted, is `kvm_xen_set_evtchn_fast`. The call trace explicitly shows it attempting to acquire a lock: `&gpc->lock`. The accompanying information `ffff888038241530 (&gpc->lock){....}-{3:3}` indicates that this lock is a `rwlock_t` and it's currently held in shared mode (`{....}-{3:3}`). Now, this is where the PREEMPT_RT aspect becomes paramount. In a PREEMPT_RT environment, `rwlock_t` implementations are designed to be *sleeping locks*. This means that if the lock is unavailable, the current task can be put to sleep (yield the CPU) until the lock is released.
The problem, therefore, is that the `xen_timer_callback` is running in a context that is effectively a hard interrupt. When `kvm_xen_set_evtchn_fast` tries to acquire the `gpc->lock` using `rt_read_lock`, and this lock is already held by something that prevents immediate acquisition, the `rt_read_lock` function attempts to sleep. However, you simply *cannot* sleep in a hard interrupt context. Sleeping requires a process context that allows rescheduling. Thus, the kernel detects this violation and reports the "sleeping function called from invalid context" bug.
My next step would be to dive into the source code for `xen_timer_callback` in `arch/x86/kvm/xen.c` to precisely understand how it's interacting with the hrtimer system and why it's being invoked in a way that leads it to call a function that attempts a sleeping lock acquisition within a hardirq. I'd be looking to see if the timer mode is incorrectly set, if there are race conditions in how the timer is armed or dispatched, or if the lock itself is being held inappropriately by another component that is also operating within interrupt context or under preemption locks that are incompatible with the hrtimer's execution path.
|
| 6/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c Name:xen_timer_callback]
Results: map[SourceCode: 126: static enum hrtimer_restart xen_timer_callback(struct hrtimer *timer)
127: {
128: struct kvm_vcpu *vcpu = container_of(timer, struct kvm_vcpu,
129: arch.xen.timer);
130: struct kvm_xen_evtchn e;
131: int rc;
132:
133: if (atomic_read(&vcpu->arch.xen.timer_pending))
134: return HRTIMER_NORESTART;
135:
136: e.vcpu_id = vcpu->vcpu_id;
137: e.vcpu_idx = vcpu->vcpu_idx;
138: e.port = vcpu->arch.xen.timer_virq;
139: e.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
140:
141: rc = kvm_xen_set_evtchn_fast(&e, vcpu->kvm);
142: if (rc != -EWOULDBLOCK) {
143: vcpu->arch.xen.timer_expires = 0;
144: return HRTIMER_NORESTART;
145: }
146:
147: atomic_inc(&vcpu->arch.xen.timer_pending);
148: kvm_make_request(KVM_REQ_UNBLOCK, vcpu);
149: kvm_vcpu_kick(vcpu);
150:
151: return HRTIMER_NORESTART;
152: }
SourceFile:arch/x86/kvm/xen.c]
|
| 7/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 10058
output: 63
thoughts: 15
Thoughts: **My Thought Process Regarding `xen_timer_callback` Initialization**
Right, so my immediate goal here is to understand precisely how the `xen_timer_callback` function gets set up. I'm not just looking for *where* it's declared, but rather the specific mechanics of its initialization – what code path leads to it being registered or made active within the Xen environment. This is crucial for understanding its timing, its context, and ultimately, how it integrates into the broader Xen scheduling and event handling mechanisms. I need to trace its lifecycle from its definition to its active deployment.
|
| 8/2 |
2026/08/12 13:19 |
tool |
codesearch-find-references |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c IncludeSnippetLines:5 Name:xen_timer_callback SourceTreePrefix:arch/x86/kvm/]
Results: map[References:[map[ReferenceKind:takes-address-of ReferencingEntityKind:function ReferencingEntityName:kvm_xen_init_vcpu SourceFile:arch/x86/kvm/xen.c SourceLine:2313 SourceSnippet:2308: {
2309: vcpu->arch.xen.vcpu_id = XEN_VCPU_ID_INVALID;
2310: vcpu->arch.xen.poll_evtchn = 0;
2311:
2312: timer_setup(&vcpu->arch.xen.poll_timer, cancel_evtchn_poll, 0);
2313: hrtimer_setup(&vcpu->arch.xen.timer, xen_timer_callback, CLOCK_MONOTONIC,
2314: HRTIMER_MODE_ABS_HARD);
2315:
2316: kvm_gpc_init(&vcpu->arch.xen.runstate_cache, vcpu->kvm);
2317: kvm_gpc_init(&vcpu->arch.xen.runstate2_cache, vcpu->kvm);
2318: kvm_gpc_init(&vcpu->arch.xen.vcpu_info_cache, vcpu->kvm);
] map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:kvm_xen_start_timer SourceFile:arch/x86/kvm/xen.c SourceLine:308 SourceSnippet: 303:
304: atomic_set(&vcpu->arch.xen.timer_pending, 0);
305: vcpu->arch.xen.timer_expires = guest_abs;
306:
307: if (delta <= 0)
308: xen_timer_callback(&vcpu->arch.xen.timer);
309: else
310: hrtimer_start(&vcpu->arch.xen.timer,
311: ktime_add_ns(kernel_now, delta),
312: HRTIMER_MODE_ABS_HARD);
313: }
]] TruncatedOutput:false]
|
| 9/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 10653
output: 47
thoughts: 75
Thoughts: **My Thought Process Regarding `kvm_xen_set_evtchn_fast` and `HRTIMER_MODE_ABS_HARD`**
Okay, so I've just encountered a specific piece of code, `kvm_xen_set_evtchn_fast`, and it's utilizing `HRTIMER_MODE_ABS_HARD`. My immediate understanding, based on my expertise in this domain, is that this hrtimer is operating within the hardirq context. This is a crucial detail because it dictates certain behaviors and constraints.
Now, my next step is to delve into `kvm_xen_set_evtchn_fast` itself. I need to scrutinize its implementation. My initial observation is that it acquires a lock, and specifically, it's a `rwlock_t`. This tells me there's a need for synchronized access to shared resources within this function. Understanding the nature of this read-write lock and how it's being used – whether for exclusive writes or shared reads – will be key to grasping the potential for contention and the overall concurrency management strategy. My focus will be on tracing the locking mechanism and its implications for the execution flow and data integrity within the context of the hardirq-driven hrtimer.
|
| 10/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c Name:kvm_xen_set_evtchn_fast]
Results: map[SourceCode:1792: /*
1793: * The return value from this function is propagated to kvm_set_irq() API,
1794: * so it returns:
1795: * < 0 Interrupt was ignored (masked or not delivered for other reasons)
1796: * = 0 Interrupt was coalesced (previous irq is still pending)
1797: * > 0 Number of CPUs interrupt was delivered to
1798: *
1799: * It is also called directly from kvm_arch_set_irq_inatomic(), where the
1800: * only check on its return value is a comparison with -EWOULDBLOCK'.
1801: */
1802: int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm)
1803: {
1804: struct gfn_to_pfn_cache *gpc = &kvm->arch.xen.shinfo_cache;
1805: struct kvm_vcpu *vcpu;
1806: unsigned long *pending_bits, *mask_bits;
1807: unsigned long flags;
1808: int port_word_bit;
1809: bool kick_vcpu = false;
1810: int vcpu_idx, idx, rc;
1811:
1812: vcpu_idx = READ_ONCE(xe->vcpu_idx);
1813: if (vcpu_idx >= 0)
1814: vcpu = kvm_get_vcpu(kvm, vcpu_idx);
1815: else {
1816: vcpu = kvm_get_vcpu_by_id(kvm, xe->vcpu_id);
1817: if (!vcpu)
1818: return -EINVAL;
1819: WRITE_ONCE(xe->vcpu_idx, vcpu->vcpu_idx);
1820: }
1821:
1822: if (xe->port >= max_evtchn_port(kvm))
1823: return -EINVAL;
1824:
1825: rc = -EWOULDBLOCK;
1826:
1827: idx = srcu_read_lock(&kvm->srcu);
1828:
1829: read_lock_irqsave(&gpc->lock, flags);
1830: if (!kvm_gpc_check(gpc, PAGE_SIZE))
1831: goto out_rcu;
1832:
1833: if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
1834: struct shared_info *shinfo = gpc->khva;
1835: pending_bits = (unsigned long *)&shinfo->evtchn_pending;
1836: mask_bits = (unsigned long *)&shinfo->evtchn_mask;
1837: port_word_bit = xe->port / 64;
1838: } else {
1839: struct compat_shared_info *shinfo = gpc->khva;
1840: pending_bits = (unsigned long *)&shinfo->evtchn_pending;
1841: mask_bits = (unsigned long *)&shinfo->evtchn_mask;
1842: port_word_bit = xe->port / 32;
1843: }
1844:
1845: /*
1846: * If this port wasn't already set, and if it isn't masked, then
1847: * we try to set the corresponding bit in the in-kernel shadow of
1848: * evtchn_pending_sel for the target vCPU. And if *that* wasn't
1849: * already set, then we kick the vCPU in question to write to the
1850: * *real* evtchn_pending_sel in its own guest vcpu_info struct.
1851: */
1852: if (test_and_set_bit(xe->port, pending_bits)) {
1853: rc = 0; /* It was already raised */
1854: } else if (test_bit(xe->port, mask_bits)) {
1855: rc = -ENOTCONN; /* Masked */
1856: kvm_xen_check_poller(vcpu, xe->port);
1857: } else {
1858: rc = 1; /* Delivered to the bitmap in shared_info. */
1859: /* Now switch to the vCPU's vcpu_info to set the index and pending_sel */
1860: read_unlock_irqrestore(&gpc->lock, flags);
1861: gpc = &vcpu->arch.xen.vcpu_info_cache;
1862:
1863: read_lock_irqsave(&gpc->lock, flags);
1864: if (!kvm_gpc_check(gpc, sizeof(struct vcpu_info))) {
1865: /*
1866: * Could not access the vcpu_info. Set the bit in-kernel
1867: * and prod the vCPU to deliver it for itself.
1868: */
1869: if (!test_and_set_bit(port_word_bit, &vcpu->arch.xen.evtchn_pending_sel))
1870: kick_vcpu = true;
1871: goto out_rcu;
1872: }
1873:
1874: if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
1875: struct vcpu_info *vcpu_info = gpc->khva;
1876: if (!test_and_set_bit(port_word_bit, &vcpu_info->evtchn_pending_sel)) {
1877: WRITE_ONCE(vcpu_info->evtchn_upcall_pending, 1);
1878: kick_vcpu = true;
1879: }
1880: } else {
1881: struct compat_vcpu_info *vcpu_info = gpc->khva;
1882: if (!test_and_set_bit(port_word_bit,
1883: (unsigned long *)&vcpu_info->evtchn_pending_sel)) {
1884: WRITE_ONCE(vcpu_info->evtchn_upcall_pending, 1);
1885: kick_vcpu = true;
1886: }
1887: }
1888:
1889: /* For the per-vCPU lapic vector, deliver it as MSI. */
1890: if (kick_vcpu && vcpu->arch.xen.upcall_vector) {
1891: kvm_xen_inject_vcpu_vector(vcpu);
1892: kick_vcpu = false;
1893: }
1894: }
1895:
1896: out_rcu:
1897: read_unlock_irqrestore(&gpc->lock, flags);
1898: srcu_read_unlock(&kvm->srcu, idx);
1899:
1900: if (kick_vcpu) {
1901: kvm_make_request(KVM_REQ_UNBLOCK, vcpu);
1902: kvm_vcpu_kick(vcpu);
1903: }
1904:
1905: return rc;
1906: }
SourceFile:arch/x86/kvm/xen.c]
|
| 11/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 12839
output: 66
thoughts: 608
Thoughts: **My Thought Process Regarding the KVM Xen Event Channel Locking Issue**
Alright, so I'm digging into this `kvm_xen_set_evtchn_fast` function, and the immediate red flag that pops up is its use of locking mechanisms, specifically in the context of PREEMPT_RT. My initial scan reveals it calls both `srcu_read_lock(&kvm->srcu)` and `read_lock_irqsave(&gpc->lock, flags)`. Now, the critical piece of information here is that both of these *can* be sleeping locks when PREEMPT_RT is enabled.
My internal monologue then corrects itself slightly: "Wait a minute, `srcu_read_lock` itself isn't a *sleeping* lock in the typical sense, but it might involve acquiring a lock." However, the more significant issue emerges with `read_lock_irqsave(&gpc->lock, flags)`. When `gpc->lock` is a `rwlock_t` and we're in a PREEMPT_RT environment, this `read_lock_irqsave` call actually resolves to `rt_read_lock`. And *that* is unequivocally a sleeping lock.
The bug report that I'm referencing directly confirms this suspicion. It explicitly states:
```
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:248
in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 5622, name: syz-executor363
```
The stack trace further pinpoints the problem:
```
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1be/0x990 arch/x86/kvm/xen.c:1827
```
This all traces back to the `rt_read_lock` call, which is indeed being invoked by `read_lock_irqsave(&gpc->lock, flags)`. The core of the problem is that `gpc->lock` is a `rwlock_t`, and in PREEMPT_RT, this maps to `rt_rw_lock`. Crucially, `rt_rw_lock` *can sleep*.
The critical context is that this is happening within `xen_timer_callback`. My understanding is that `xen_timer_callback` is executed in a hardirq context because it's the callback for an hrtimer (`vcpu->arch.xen.timer`). Therefore, calling a sleeping lock (`rt_read_lock`) from this hardirq context is fundamentally invalid under PREEMPT_RT and leads to the observed BUG.
The next logical step in my analysis is to figure out how this situation arises. How can I reliably trigger `xen_timer_callback` within a hardirq context? My immediate thought is to trace back where `xen_timer_callback` is initiated. It's the callback for `vcpu->arch.xen.timer`, so I need to examine when and how `kvm_xen_start_timer` is called. That's the entry point to understanding the reproducers.
|
| 12/2 |
2026/08/12 13:19 |
tool |
codesearch-find-references |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c IncludeSnippetLines:5 Name:kvm_xen_start_timer SourceTreePrefix:arch/x86/kvm/]
Results: map[References:[map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:kvm_xen_hcall_set_timer_op SourceFile:arch/x86/kvm/xen.c SourceLine:1673 SourceSnippet:1668: {
1669: if (!kvm_xen_timer_enabled(vcpu))
1670: return false;
1671:
1672: if (timeout)
1673: kvm_xen_start_timer(vcpu, timeout, true);
1674: else
1675: kvm_xen_stop_timer(vcpu);
1676:
1677: *r = 0;
1678: return true;
] map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:kvm_xen_hcall_vcpu_op SourceFile:arch/x86/kvm/xen.c SourceLine:1657 SourceSnippet:1652: sizeof(struct compat_vcpu_set_singleshot_timer), &e)) {
1653: *r = -EFAULT;
1654: return true;
1655: }
1656:
1657: kvm_xen_start_timer(vcpu, oneshot.timeout_abs_ns, false);
1658: } else {
1659: kvm_xen_stop_timer(vcpu);
1660: }
1661:
1662: *r = 0;
] map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:kvm_xen_vcpu_set_attr SourceFile:arch/x86/kvm/xen.c SourceLine:1130 SourceSnippet:1125: kvm_xen_stop_timer(vcpu);
1126: vcpu->arch.xen.timer_virq = data->u.timer.port;
1127:
1128: /* Start the timer if the new value has a valid vector+expiry. */
1129: if (data->u.timer.port && data->u.timer.expires_ns)
1130: kvm_xen_start_timer(vcpu, data->u.timer.expires_ns, false);
1131:
1132: r = 0;
1133: break;
1134:
1135: case KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR:
]] TruncatedOutput:false]
|
| 13/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 14134
output: 47
thoughts: 37
Thoughts: **The Genesis of an Idea: Uncovering a Timer's Activation**
My train of thought began with a sudden realization, a spark of insight regarding the function `kvm_xen_vcpu_set_attr`. I understood, with a degree of certainty, that this particular function was capable of initiating a timer. This wasn't a vague suspicion; it felt like a concrete piece of knowledge, a discovered mechanism. Immediately, my focus narrowed. The next logical step, the imperative action, was to delve directly into the source code, to scrutinize `kvm_xen_vcpu_set_attr` itself. I needed to confirm this hypothesis, to trace the execution flow and verify precisely *how* and *when* this timer activation occurred within its implementation. My objective was clear: understand the inner workings of this function and validate my initial, potent understanding of its role in timer management.
|
| 14/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c Name:kvm_xen_vcpu_set_attr]
Results: map[SourceCode: 907: int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
908: {
909: int idx, r = -ENOENT;
910:
911: mutex_lock(&vcpu->kvm->arch.xen.xen_lock);
912: idx = srcu_read_lock(&vcpu->kvm->srcu);
913:
914: switch (data->type) {
915: case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO:
916: case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA:
917: /* No compat necessary here. */
918: BUILD_BUG_ON(sizeof(struct vcpu_info) !=
919: sizeof(struct compat_vcpu_info));
920: BUILD_BUG_ON(offsetof(struct vcpu_info, time) !=
921: offsetof(struct compat_vcpu_info, time));
922:
923: if (data->type == KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO) {
924: if (data->u.gpa == KVM_XEN_INVALID_GPA) {
925: kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
926: r = 0;
927: break;
928: }
929:
930: r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_info_cache,
931: data->u.gpa, sizeof(struct vcpu_info));
932: } else {
933: if (data->u.hva == 0) {
934: kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
935: r = 0;
936: break;
937: }
938:
939: r = kvm_gpc_activate_hva(&vcpu->arch.xen.vcpu_info_cache,
940: data->u.hva, sizeof(struct vcpu_info));
941: }
942:
943: if (!r)
944: kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
945:
946: break;
947:
948: case KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO:
949: if (data->u.gpa == KVM_XEN_INVALID_GPA) {
950: kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_time_info_cache);
951: r = 0;
952: break;
953: }
954:
955: r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_time_info_cache,
956: data->u.gpa,
957: sizeof(struct pvclock_vcpu_time_info));
958: if (!r)
959: kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
960: break;
961:
962: case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADDR: {
963: size_t sz, sz1, sz2;
964:
965: if (!sched_info_on()) {
966: r = -EOPNOTSUPP;
967: break;
968: }
969: if (data->u.gpa == KVM_XEN_INVALID_GPA) {
970: r = 0;
971: deactivate_out:
972: kvm_gpc_deactivate(&vcpu->arch.xen.runstate_cache);
973: kvm_gpc_deactivate(&vcpu->arch.xen.runstate2_cache);
974: break;
975: }
976:
977: /*
978: * If the guest switches to 64-bit mode after setting the runstate
979: * address, that's actually OK. kvm_xen_update_runstate_guest()
980: * will cope.
981: */
982: if (IS_ENABLED(CONFIG_64BIT) && vcpu->kvm->arch.xen.long_mode)
983: sz = sizeof(struct vcpu_runstate_info);
984: else
985: sz = sizeof(struct compat_vcpu_runstate_info);
986:
987: /* How much fits in the (first) page? */
988: sz1 = PAGE_SIZE - (data->u.gpa & ~PAGE_MASK);
989: r = kvm_gpc_activate(&vcpu->arch.xen.runstate_cache,
990: data->u.gpa, sz1);
991: if (r)
992: goto deactivate_out;
993:
994: /* Either map the second page, or deactivate the second GPC */
995: if (sz1 >= sz) {
996: kvm_gpc_deactivate(&vcpu->arch.xen.runstate2_cache);
997: } else {
998: sz2 = sz - sz1;
999: BUG_ON((data->u.gpa + sz1) & ~PAGE_MASK);
1000: r = kvm_gpc_activate(&vcpu->arch.xen.runstate2_cache,
1001: data->u.gpa + sz1, sz2);
1002: if (r)
1003: goto deactivate_out;
1004: }
1005:
1006: kvm_xen_update_runstate_guest(vcpu, false);
1007: break;
1008: }
1009: case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_CURRENT:
1010: if (!sched_info_on()) {
1011: r = -EOPNOTSUPP;
1012: break;
1013: }
1014: if (data->u.runstate.state > RUNSTATE_offline) {
1015: r = -EINVAL;
1016: break;
1017: }
1018:
1019: kvm_xen_update_runstate(vcpu, data->u.runstate.state);
1020: r = 0;
1021: break;
1022:
1023: case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_DATA:
1024: if (!sched_info_on()) {
1025: r = -EOPNOTSUPP;
1026: break;
1027: }
1028: if (data->u.runstate.state > RUNSTATE_offline) {
1029: r = -EINVAL;
1030: break;
1031: }
1032: if (data->u.runstate.state_entry_time !=
1033: (data->u.runstate.time_running +
1034: data->u.runstate.time_runnable +
1035: data->u.runstate.time_blocked +
1036: data->u.runstate.time_offline)) {
1037: r = -EINVAL;
1038: break;
1039: }
1040: if (get_kvmclock_ns(vcpu->kvm) <
1041: data->u.runstate.state_entry_time) {
1042: r = -EINVAL;
1043: break;
1044: }
1045:
1046: vcpu->arch.xen.current_runstate = data->u.runstate.state;
1047: vcpu->arch.xen.runstate_entry_time =
1048: data->u.runstate.state_entry_time;
1049: vcpu->arch.xen.runstate_times[RUNSTATE_running] =
1050: data->u.runstate.time_running;
1051: vcpu->arch.xen.runstate_times[RUNSTATE_runnable] =
1052: data->u.runstate.time_runnable;
1053: vcpu->arch.xen.runstate_times[RUNSTATE_blocked] =
1054: data->u.runstate.time_blocked;
1055: vcpu->arch.xen.runstate_times[RUNSTATE_offline] =
1056: data->u.runstate.time_offline;
1057: vcpu->arch.xen.last_steal = current->sched_info.run_delay;
1058: r = 0;
1059: break;
1060:
1061: case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST:
1062: if (!sched_info_on()) {
1063: r = -EOPNOTSUPP;
1064: break;
1065: }
1066: if (data->u.runstate.state > RUNSTATE_offline &&
1067: data->u.runstate.state != (u64)-1) {
1068: r = -EINVAL;
1069: break;
1070: }
1071: /* The adjustment must add up */
1072: if (data->u.runstate.state_entry_time !=
1073: (data->u.runstate.time_running +
1074: data->u.runstate.time_runnable +
1075: data->u.runstate.time_blocked +
1076: data->u.runstate.time_offline)) {
1077: r = -EINVAL;
1078: break;
1079: }
1080:
1081: if (get_kvmclock_ns(vcpu->kvm) <
1082: (vcpu->arch.xen.runstate_entry_time +
1083: data->u.runstate.state_entry_time)) {
1084: r = -EINVAL;
1085: break;
1086: }
1087:
1088: vcpu->arch.xen.runstate_entry_time +=
1089: data->u.runstate.state_entry_time;
1090: vcpu->arch.xen.runstate_times[RUNSTATE_running] +=
1091: data->u.runstate.time_running;
1092: vcpu->arch.xen.runstate_times[RUNSTATE_runnable] +=
1093: data->u.runstate.time_runnable;
1094: vcpu->arch.xen.runstate_times[RUNSTATE_blocked] +=
1095: data->u.runstate.time_blocked;
1096: vcpu->arch.xen.runstate_times[RUNSTATE_offline] +=
1097: data->u.runstate.time_offline;
1098:
1099: if (data->u.runstate.state <= RUNSTATE_offline)
1100: kvm_xen_update_runstate(vcpu, data->u.runstate.state);
1101: else if (vcpu->arch.xen.runstate_cache.active)
1102: kvm_xen_update_runstate_guest(vcpu, false);
1103: r = 0;
1104: break;
1105:
1106: case KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID:
1107: BUILD_BUG_ON(XEN_VCPU_ID_INVALID < KVM_MAX_VCPUS);
1108:
1109: if (data->u.vcpu_id >= KVM_MAX_VCPUS)
1110: r = -EINVAL;
1111: else {
1112: vcpu->arch.xen.vcpu_id = data->u.vcpu_id;
1113: r = 0;
1114: }
1115: break;
1116:
1117: case KVM_XEN_VCPU_ATTR_TYPE_TIMER:
1118: if (data->u.timer.port &&
1119: data->u.timer.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL) {
1120: r = -EINVAL;
1121: break;
1122: }
1123:
1124: /* Stop the timer (if it's running) before changing the vector */
1125: kvm_xen_stop_timer(vcpu);
1126: vcpu->arch.xen.timer_virq = data->u.timer.port;
1127:
1128: /* Start the timer if the new value has a valid vector+expiry. */
1129: if (data->u.timer.port && data->u.timer.expires_ns)
1130: kvm_xen_start_timer(vcpu, data->u.timer.expires_ns, false);
1131:
1132: r = 0;
1133: break;
1134:
1135: case KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR:
1136: if (data->u.vector && data->u.vector < 0x10)
1137: r = -EINVAL;
1138: else {
1139: vcpu->arch.xen.upcall_vector = data->u.vector;
1140: r = 0;
1141: }
1142: break;
1143:
1144: default:
1145: break;
1146: }
1147:
1148: srcu_read_unlock(&vcpu->kvm->srcu, idx);
1149: mutex_unlock(&vcpu->kvm->arch.xen.xen_lock);
1150: return r;
1151: }
SourceFile:arch/x86/kvm/xen.c]
|
| 15/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 18282
output: 44
thoughts: 134
Thoughts: **My Thought Process Regarding KVM Xen VCPU Timers**
My initial thought is that I can leverage the `KVM_XEN_VCPU_SET_ATTR` ioctl, specifically targeting a VCPU file descriptor with `KVM_XEN_VCPU_ATTR_TYPE_TIMER`, to establish a timer.
However, I then recall that the function `kvm_xen_start_timer` is the one actually responsible for setting this timer, and it uses the `data->u.timer.expires_ns` field to determine the expiration time.
This leads me to a crucial consideration: what happens if I set the expiration time to a value that's already in the past? My expectation is that if the specified expiration time is in the past, the timer should fire immediately.
This immediate firing raises a potential concern: could the timer's execution be synchronous within the `kvm_xen_start_timer` function itself? To resolve this uncertainty and understand the precise behavior, I need to delve into the implementation details of `kvm_xen_start_timer`.
|
| 16/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c Name:kvm_xen_start_timer]
Results: map[SourceCode: 187: static void kvm_xen_start_timer(struct kvm_vcpu *vcpu, u64 guest_abs,
188: bool linux_wa)
189: {
190: struct kvm_vcpu_xen *xen = &vcpu->arch.xen;
191: int64_t kernel_now, delta;
192: uint64_t guest_now;
193: int r = -EOPNOTSUPP;
194:
195: /*
196: * The guest provides the requested timeout in absolute nanoseconds
197: * of the KVM clock — as *it* sees it, based on the scaled TSC and
198: * the pvclock information provided by KVM.
199: *
200: * The kernel doesn't support hrtimers based on CLOCK_MONOTONIC_RAW
201: * so use CLOCK_MONOTONIC. In the timescales covered by timers, the
202: * difference won't matter much as there is no cumulative effect.
203: *
204: * Calculate the time for some arbitrary point in time around "now"
205: * in terms of both kvmclock and CLOCK_MONOTONIC. Calculate the
206: * delta between the kvmclock "now" value and the guest's requested
207: * timeout, apply the "Linux workaround" described below, and add
208: * the resulting delta to the CLOCK_MONOTONIC "now" value, to get
209: * the absolute CLOCK_MONOTONIC time at which the timer should
210: * fire.
211: */
212: do {
213: struct pvclock_vcpu_time_info hv_clock;
214: uint64_t host_tsc, guest_tsc;
215:
216: if (!cpu_feature_enabled(X86_FEATURE_CONSTANT_TSC) ||
217: !vcpu->kvm->arch.use_master_clock)
218: break;
219:
220: /*
221: * If both Xen PV clocks are active, arbitrarily try to use the
222: * compat clock first, but also try to use the non-compat clock
223: * if the compat clock is unusable. The two PV clocks hold the
224: * same information, but it's possible one (or both) is stale
225: * and/or currently unreachable.
226: */
227: if (xen->vcpu_info_cache.active)
228: r = xen_get_guest_pvclock(vcpu, &hv_clock, &xen->vcpu_info_cache,
229: offsetof(struct compat_vcpu_info, time));
230: if (r && xen->vcpu_time_info_cache.active)
231: r = xen_get_guest_pvclock(vcpu, &hv_clock, &xen->vcpu_time_info_cache, 0);
232: if (r)
233: break;
234:
235: if (!IS_ENABLED(CONFIG_64BIT) ||
236: !kvm_get_monotonic_and_clockread(&kernel_now, &host_tsc)) {
237: /*
238: * Don't fall back to get_kvmclock_ns() because it's
239: * broken; it has a systemic error in its results
240: * because it scales directly from host TSC to
241: * nanoseconds, and doesn't scale first to guest TSC
242: * and *then* to nanoseconds as the guest does.
243: *
244: * There is a small error introduced here because time
245: * continues to elapse between the ktime_get() and the
246: * subsequent rdtsc(). But not the systemic drift due
247: * to get_kvmclock_ns().
248: */
249: kernel_now = ktime_get(); /* This is CLOCK_MONOTONIC */
250: host_tsc = rdtsc();
251: }
252:
253: /* Calculate the guest kvmclock as the guest would do it. */
254: guest_tsc = kvm_read_l1_tsc(vcpu, host_tsc);
255: guest_now = __pvclock_read_cycles(&hv_clock, guest_tsc);
256: } while (0);
257:
258: if (r) {
259: /*
260: * Without CONSTANT_TSC, get_kvmclock_ns() is the only option.
261: *
262: * Also if the guest PV clock hasn't been set up yet, as is
263: * likely to be the case during migration when the vCPU has
264: * not been run yet. It would be possible to calculate the
265: * scaling factors properly in that case but there's not much
266: * point in doing so. The get_kvmclock_ns() drift accumulates
267: * over time, so it's OK to use it at startup. Besides, on
268: * migration there's going to be a little bit of skew in the
269: * precise moment at which timers fire anyway. Often they'll
270: * be in the "past" by the time the VM is running again after
271: * migration.
272: */
273: guest_now = get_kvmclock_ns(vcpu->kvm);
274: kernel_now = ktime_get();
275: }
276:
277: delta = guest_abs - guest_now;
278:
279: /*
280: * Xen has a 'Linux workaround' in do_set_timer_op() which checks for
281: * negative absolute timeout values (caused by integer overflow), and
282: * for values about 13 days in the future (2^50ns) which would be
283: * caused by jiffies overflow. For those cases, Xen sets the timeout
284: * 100ms in the future (not *too* soon, since if a guest really did
285: * set a long timeout on purpose we don't want to keep churning CPU
286: * time by waking it up). Emulate Xen's workaround when starting the
287: * timer in response to __HYPERVISOR_set_timer_op.
288: */
289: if (linux_wa &&
290: unlikely((int64_t)guest_abs < 0 ||
291: (delta > 0 && (uint32_t) (delta >> 50) != 0))) {
292: delta = 100 * NSEC_PER_MSEC;
293: guest_abs = guest_now + delta;
294: }
295:
296: /*
297: * Avoid races with the old timer firing. Checking timer_expires
298: * to avoid calling hrtimer_cancel() will only have false positives
299: * so is fine.
300: */
301: if (vcpu->arch.xen.timer_expires)
302: hrtimer_cancel(&vcpu->arch.xen.timer);
303:
304: atomic_set(&vcpu->arch.xen.timer_pending, 0);
305: vcpu->arch.xen.timer_expires = guest_abs;
306:
307: if (delta <= 0)
308: xen_timer_callback(&vcpu->arch.xen.timer);
309: else
310: hrtimer_start(&vcpu->arch.xen.timer,
311: ktime_add_ns(kernel_now, delta),
312: HRTIMER_MODE_ABS_HARD);
313: }
SourceFile:arch/x86/kvm/xen.c]
|
| 17/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 20715
output: 45
thoughts: 893
Thoughts: **My Thought Process Unpacking the Xen Timer Bug**
Okay, let me walk through how I've been dissecting this Xen timer issue. It's a classic case of context sensitivity and locking, as you'd expect.
Initially, my understanding was that if the `delta` calculation resulted in a non-positive value (`<= 0`), the system would bypass the asynchronous timer mechanism and directly invoke `xen_timer_callback`. Now, if that were the case, the callback would be executing within the context of `kvm_xen_vcpu_set_attr`, which originates from a syscall. And that's not a problem, because `rt_read_lock` is perfectly permissible within a syscall context. My initial thought was, "No issue here."
However, the bug report paints a very different picture. The crash is clearly occurring in a hardirq context, as evidenced by the call trace provided:
```
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
__might_resched+0x329/0x480 kernel/sched/core.c:9194
rt_read_lock+0xa9/0x4b0 kernel/locking/spinlock_rt.c:248 <-- Aha! The problematic lock
kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x3a0/0xaf0 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x44a/0x900 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
```
Seeing `rt_read_lock` in a hardirq context immediately flags it as a potential deadlock or race condition. This is because hardirq context can preempt other interrupt handlers, and `rt_read_lock` is designed for contexts where preemption is managed, not for the unpredictable nature of hardirqs.
So, my revised thought is: we *need* `delta > 0` to ensure that `hrtimer_start` is actually called. This is the pathway that leads to the timer firing asynchronously. And it's precisely *when* this asynchronous timer fires in the hardirq context that the `rt_read_lock` is invoked, triggering the crash. The very mechanism intended to defer the operation into a safe context is precisely what's causing the problem.
This leads me to the reproduction steps. To trigger this, I need to set up the KVM environment appropriately.
1. **Create a KVM VM:** The fundamental building block.
2. **Create a VCPU:** Essential for KVM operations.
3. **Set `KVM_XEN_VCPU_ATTR_TYPE_TIMER`:** This is the key attribute that configures the Xen timer callback.
* **Crucially**, the `data->u.timer.port` must be non-zero. If it's zero, the direct callback path might be taken, which we've already established isn't the problematic one.
* And `data->u.timer.expires_ns` needs to be set to a future expiration time.
Now, here's a bit of a rabbit hole I'm exploring regarding `expires_ns`. It's specified as an *absolute time in guest kvmclock*. This means I can't just pick an arbitrary future timestamp. I need to know the current guest `kvmclock` value to correctly calculate a future expiration.
My initial thought was to just set it to a very small future value. But then I realized that a small `delta` (the difference between the current `kvmclock` and the desired `expires_ns`) might again lead to `delta <= 0`, bypassing the hardirq timer. Conversely, setting it to a very large future value might make it take too long to test reliably.
The critical piece of information I need is how `guest_now` is determined. The text mentions it's calculated using `get_kvmclock_ns(vcpu->kvm)`. My next step is to dive into the `get_kvmclock_ns` implementation. Does it indeed start from zero when the VM is created? If so, I can confidently set `expires_ns` to something like `100,000,000` (100ms) and expect `delta` to be positive, thus forcing the `hrtimer_start` call and subsequently the hardirq context timer expiration, reproducing the bug. This seems to be the most direct path to reliably trigger the race.
|
| 18/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/x86.c Name:get_kvmclock_ns]
Results: map[SourceCode:1707: u64 get_kvmclock_ns(struct kvm *kvm)
1708: {
1709: struct kvm_clock_data data;
1710:
1711: get_kvmclock(kvm, &data);
1712: return data.clock;
1713: }
SourceFile:arch/x86/kvm/x86.c]
|
| 19/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 21765
output: 43
thoughts: 11
Thoughts: **My Thought Process on `get_kvmclock`**
Alright, so the first thing I'm doing is diving into `get_kvmclock`. My immediate goal here is to understand exactly how this function works, what it's designed to do, and crucially, what its outputs are. Given my expertise, I'm not just looking for a surface-level explanation; I want to dissect its internal workings. I'm thinking about the underlying mechanisms it leverages, the specific KVM (Kernel-based Virtual Machine) interfaces it interacts with, and the precise data it retrieves. Is it fetching raw clock cycles, a time offset, or something more complex? I'm also considering the context in which this function would be used – what kind of operations or analyses would necessitate this specific clock information? Is it for performance monitoring, synchronization, or perhaps debugging virtualized environments? I'll be paying close attention to any potential edge cases or limitations it might have, and how it handles errors or unexpected states. Ultimately, I'm aiming for a comprehensive grasp of its functionality, its dependencies, and its implications within the broader system it operates.
|
| 20/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/x86.c Name:get_kvmclock]
Results: map[SourceCode:1696: static void get_kvmclock(struct kvm *kvm, struct kvm_clock_data *data)
1697: {
1698: struct kvm_arch *ka = &kvm->arch;
1699: unsigned seq;
1700:
1701: do {
1702: seq = read_seqcount_begin(&ka->pvclock_sc);
1703: __get_kvmclock(kvm, data);
1704: } while (read_seqcount_retry(&ka->pvclock_sc, seq));
1705: }
SourceFile:arch/x86/kvm/x86.c]
|
| 21/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 21999
output: 44
thoughts: 12
Thoughts: **My Thought Process Regarding `__get_kvmclock`**
Alright, so I'm looking at this `__get_kvmclock` function. My immediate thought is to understand its purpose and how it integrates with the broader system, particularly in the context of KVM virtualization. I'm assuming this is a low-level kernel function, likely involved in managing timekeeping within a KVM guest environment.
My first step is to dissect its signature and any immediate comments. What arguments does it take? What does it return? Are there any inline explanations that give a quick hint about what it's doing? This will set the stage for a more detailed analysis.
Then, I'll trace the execution flow. I want to follow the logic step by step. What are the conditional branches? What data structures is it accessing or modifying? Is it interacting with any hardware registers, or is it purely dealing with software state? I'll be paying close attention to any calls to other kernel functions, as these will reveal dependencies and the larger picture of its operation.
My primary concern is understanding how KVM clock information is retrieved or updated. Is this function responsible for reading the guest's current time, or is it involved in synchronizing the guest's clock with the host's clock? Does it handle any specific clock sources, like the TSC (Timestamp Counter) or other architectural timers? I need to ascertain if it's a read-only operation or if it has any side effects on the system's timekeeping.
I'm also considering the implications of this function in different scenarios. What happens if KVM is not enabled? Does this function behave differently? What about different CPU architectures or guest operating systems? Understanding these variations is crucial for a robust comprehension.
Finally, I'll be looking for potential pitfalls or areas of interest. Are there any race conditions or synchronization issues I should be aware of? Are there any performance implications associated with calling this function? Is this function part of a larger clock synchronization mechanism, and if so, where does it fit in?
In essence, my goal is to build a comprehensive mental model of `__get_kvmclock`, understanding its role, its implementation details, and its impact on the timekeeping within a KVM virtualized environment.
|
| 22/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/x86.c Name:__get_kvmclock]
Results: map[SourceCode:1660: /* Called within read_seqcount_begin/retry for kvm->pvclock_sc. */
1661: static void __get_kvmclock(struct kvm *kvm, struct kvm_clock_data *data)
1662: {
1663: struct kvm_arch *ka = &kvm->arch;
1664: struct pvclock_vcpu_time_info hv_clock;
1665:
1666: /* both __this_cpu_read() and rdtsc() should be on the same cpu */
1667: get_cpu();
1668:
1669: data->flags = 0;
1670: if (ka->use_master_clock &&
1671: (cpu_feature_enabled(X86_FEATURE_CONSTANT_TSC) || __this_cpu_read(cpu_tsc_khz))) {
1672: #ifdef CONFIG_X86_64
1673: struct timespec64 ts;
1674:
1675: if (kvm_get_walltime_and_clockread(&ts, &data->host_tsc)) {
1676: data->realtime = ts.tv_nsec + NSEC_PER_SEC * ts.tv_sec;
1677: data->flags |= KVM_CLOCK_REALTIME | KVM_CLOCK_HOST_TSC;
1678: } else
1679: #endif
1680: data->host_tsc = rdtsc();
1681:
1682: data->flags |= KVM_CLOCK_TSC_STABLE;
1683: hv_clock.tsc_timestamp = ka->master_cycle_now;
1684: hv_clock.system_time = ka->master_kernel_ns + ka->kvmclock_offset;
1685: kvm_get_time_scale(NSEC_PER_SEC, get_cpu_tsc_khz() * 1000LL,
1686: &hv_clock.tsc_shift,
1687: &hv_clock.tsc_to_system_mul);
1688: data->clock = __pvclock_read_cycles(&hv_clock, data->host_tsc);
1689: } else {
1690: data->clock = get_kvmclock_base_ns() + ka->kvmclock_offset;
1691: }
1692:
1693: put_cpu();
1694: }
SourceFile:arch/x86/kvm/x86.c]
|
| 23/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 22736
output: 46
thoughts: 77
Thoughts: **My Thought Process Regarding KVM Clock Synchronization**
Okay, so my initial understanding is that `get_kvmclock_base_ns()` is essentially a direct call to `ktime_get_boottime_ns()`. This implies that the KVM clock, at its base, is derived directly from the host's boot time. That makes a certain intuitive sense – we're looking for a stable reference point.
However, a crucial detail that just surfaced is the existence of `ka->kvmclock_offset`. This value is populated when the Virtual Machine is initialized. This is a significant point because it suggests that the KVM clock isn't *just* the host's boottime. There's an additional offset being applied. My next step is to delve into the `kvm_arch_init_vm` function to understand precisely how and when this offset is calculated and applied. This will be key to understanding the full picture of how the KVM clock is managed and synchronized.
|
| 24/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/x86.c Name:kvm_arch_init_vm]
Results: map[SourceCode:9821: int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
9822: {
9823: int ret;
9824: unsigned long flags;
9825:
9826: if (!kvm_is_vm_type_supported(type))
9827: return -EINVAL;
9828:
9829: kvm->arch.vm_type = type;
9830: kvm->arch.has_private_mem =
9831: (type == KVM_X86_SW_PROTECTED_VM);
9832: /* Decided by the vendor code for other VM types. */
9833: kvm->arch.pre_fault_allowed =
9834: type == KVM_X86_DEFAULT_VM || type == KVM_X86_SW_PROTECTED_VM;
9835: kvm->arch.disabled_quirks = kvm_caps.inapplicable_quirks & kvm_caps.supported_quirks;
9836:
9837: ret = kvm_page_track_init(kvm);
9838: if (ret)
9839: goto out;
9840:
9841: ret = kvm_mmu_init_vm(kvm);
9842: if (ret)
9843: goto out_cleanup_page_track;
9844:
9845: ret = kvm_x86_call(vm_init)(kvm);
9846: if (ret)
9847: goto out_uninit_mmu;
9848:
9849: atomic_set(&kvm->arch.noncoherent_dma_count, 0);
9850:
9851: raw_spin_lock_init(&kvm->arch.tsc_write_lock);
9852: mutex_init(&kvm->arch.apic_map_lock);
9853: seqcount_raw_spinlock_init(&kvm->arch.pvclock_sc, &kvm->arch.tsc_write_lock);
9854: ratelimit_state_init(&kvm->arch.kvmclock_update_rs, HZ, 10);
9855: ratelimit_set_flags(&kvm->arch.kvmclock_update_rs, RATELIMIT_MSG_ON_RELEASE);
9856: kvm->arch.kvmclock_offset = -get_kvmclock_base_ns();
9857:
9858: raw_spin_lock_irqsave(&kvm->arch.tsc_write_lock, flags);
9859: pvclock_update_vm_gtod_copy(kvm);
9860: raw_spin_unlock_irqrestore(&kvm->arch.tsc_write_lock, flags);
9861:
9862: kvm->arch.default_tsc_khz = max_tsc_khz ? : tsc_khz;
9863: kvm->arch.apic_bus_cycle_ns = APIC_BUS_CYCLE_NS_DEFAULT;
9864: kvm->arch.guest_can_read_msr_platform_info = true;
9865: kvm->arch.enable_pmu = enable_pmu && !kvm->arch.has_protected_pmu;
9866:
9867: #if IS_ENABLED(CONFIG_HYPERV)
9868: spin_lock_init(&kvm->arch.hv_root_tdp_lock);
9869: kvm->arch.hv_root_tdp = INVALID_PAGE;
9870: #endif
9871:
9872: kvm_apicv_init(kvm);
9873: kvm_hv_init_vm(kvm);
9874: kvm_xen_init_vm(kvm);
9875:
9876: if (ignore_msrs && !report_ignored_msrs) {
9877: pr_warn_once("Running KVM with ignore_msrs=1 and report_ignored_msrs=0 is not a\n"
9878: "a supported configuration. Lying to the guest about the existence of MSRs\n"
9879: "may cause the guest operating system to hang or produce errors. If a guest\n"
9880: "does not run without ignore_msrs=1, please report it to kvm@vger.kernel.org.\n");
9881: }
9882:
9883: once_init(&kvm->arch.nx_once);
9884: return 0;
9885:
9886: out_uninit_mmu:
9887: kvm_mmu_uninit_vm(kvm);
9888: out_cleanup_page_track:
9889: kvm_page_track_cleanup(kvm);
9890: out:
9891: return ret;
9892: }
SourceFile:arch/x86/kvm/x86.c]
|
| 25/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 24229
output: 63
thoughts: 132
Thoughts: **My Thought Process Regarding KVM Clock Initialization and Timer Expirations**
My initial observation, upon seeing the line `kvm->arch.kvmclock_offset = -get_kvmclock_base_ns();`, immediately led me to a crucial deduction: that the sum `get_kvmclock_base_ns() + ka->kvmclock_offset` will evaluate to zero upon the creation of a KVM virtual machine. This implies that the guest's KVM clock is effectively initialized to zero at VM boot.
This realization is quite significant. If the guest clock starts at zero, then setting a future expiration time for a timer, such as `expires_ns` to a value like 10,000,000 nanoseconds (which is equivalent to 10 milliseconds), becomes a straightforward operation. This value will unequivocally represent a point in time *after* the current guest clock time, ensuring the timer will indeed expire in the future as intended.
To solidify my understanding and to investigate the specific context of this timer functionality, my next logical step is to examine the definition of `KVM_XEN_VCPU_ATTR_TYPE_TIMER`. I need to see how this timer attribute is structured and how it interacts with the underlying KVM clock mechanisms to ensure my assumptions about expiration are correct and to explore any potential nuances or constraints.
|
| 26/2 |
2026/08/12 13:19 |
tool |
codesearch-find-references |
0m
Error:
Args: map[ContextFile:arch/x86/kvm/xen.c IncludeSnippetLines:5 Name:KVM_XEN_VCPU_ATTR_TYPE_TIMER SourceTreePrefix:]
Results: map[References:<nil> TruncatedOutput:false]
|
| 27/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 24423
output: 45
thoughts: 15
Thoughts: **My Thought Process:**
Right, so I'm looking at this and my immediate instinct, given the context and the general structure, is that I'm dealing with a macro. My brain instantly jumps to the most efficient way to handle this type of analysis, which, for me, is definitely using grepper. It's the go-to tool for quickly scanning and extracting relevant information from code or text, and that's precisely what I need to do here. So, yeah, the plan is to leverage grepper to dive in and get what I need.
|
| 28/2 |
2026/08/12 13:19 |
tool |
grepper |
0m
Error:
Args: map[Expression:KVM_XEN_VCPU_ATTR_TYPE_TIMER PathPrefix:include/uapi/linux/kvm.h]
Results:
|
| 29/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 24481
output: 41
thoughts: 33
Thoughts: **My Thought Process:**
Okay, so I'm trying to get a handle on this KVM/Xen interaction, and I need to pinpoint where exactly the Xen-specific virtual CPU attributes are defined within the KVM kernel headers. My immediate instinct is to leverage the existing structure of KVM's header files. Given the naming convention I've seen so far (like `KVM_` prefixes for various KVM-related definitions), I'm assuming there will be a specific constant or structure related to Xen VCPU attributes.
Therefore, my next logical step is to perform a targeted search within the KVM header directory, specifically within `include/uapi/linux/kvm.h`. This file is the user-space API header for KVM, and it's the most likely place to find definitions that are exposed to userspace tools that interact with KVM. I'm specifically looking for the identifier `KVM_XEN_VCPU_ATTR`. If this symbol exists, it will likely be an enum value, a `#define`, or the start of a structure definition that encapsulates these Xen-specific VCPU attributes. This targeted search will hopefully quickly reveal the exact definition I'm looking for, allowing me to understand how these attributes are exposed and manipulated.
|
| 30/2 |
2026/08/12 13:19 |
tool |
grepper |
0m
Error:
Args: map[Expression:KVM_XEN_VCPU_ATTR PathPrefix:include/uapi/linux/kvm.h]
Results:
|
| 31/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 24553
output: 34
thoughts: 28
Thoughts: **My Internal Monologue Regarding `include/uapi/linux/kvm.h`**
Alright, I've been staring at `include/uapi/linux/kvm.h` for a bit now, and a nagging doubt is creeping in. Is this *really* where I should be looking for what I need? It feels... specific. Too specific, perhaps, to the KVM API itself. My instinct is that whatever I'm trying to find – and I need to be precise in my own mind about that, though the immediate thought is just a general "this thing related to KVM interaction" – might be more broadly applicable, or perhaps defined at a different level of abstraction within the kernel's header file hierarchy.
So, before I commit to this path, before I dive deeper into the intricacies of KVM's user-space API headers, I think the most pragmatic next step is to cast a wider net. I need to perform a global search. I'm not just going to limit myself to the `include/uapi/linux/kvm.h` directory anymore. I want to see where else this concept, this specific definition or structure, might be declared or referenced across the *entire* kernel source tree. This isn't about brute force; it's about ensuring I'm not missing a more fundamental or a more generally relevant definition that could be lurking in a header file I haven't even considered yet. My hypothesis is that by broadening the search, I'll either confirm `kvm.h` is correct (by seeing it referenced widely in context) or, more likely, uncover the *actual* location that serves as the true source of truth for this element. This is a critical step for maintaining code integrity and ensuring I'm building upon the right foundations.
|
| 32/2 |
2026/08/12 13:19 |
tool |
grepper |
0m
Args: map[Expression:KVM_XEN_VCPU_ATTR_TYPE_TIMER PathPrefix:]
Results: map[Output:Documentation/virt/kvm/api.rst=5793=KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID
--
Documentation/virt/kvm/api.rst-5798-
Documentation/virt/kvm/api.rst:5799:KVM_XEN_VCPU_ATTR_TYPE_TIMER
Documentation/virt/kvm/api.rst-5800- This attribute is available when the KVM_CAP_XEN_HVM ioctl indicates
--
arch/x86/include/uapi/asm/kvm.h=670=struct kvm_xen_vcpu_attr {
--
arch/x86/include/uapi/asm/kvm.h-704-#define KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID 0x6
arch/x86/include/uapi/asm/kvm.h:705:#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
arch/x86/include/uapi/asm/kvm.h-706-#define KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR 0x8
--
arch/x86/kvm/xen.c=907=int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
--
arch/x86/kvm/xen.c-1116-
arch/x86/kvm/xen.c:1117: case KVM_XEN_VCPU_ATTR_TYPE_TIMER:
arch/x86/kvm/xen.c-1118- if (data->u.timer.port &&
--
arch/x86/kvm/xen.c=1153=int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
--
arch/x86/kvm/xen.c-1231-
arch/x86/kvm/xen.c:1232: case KVM_XEN_VCPU_ATTR_TYPE_TIMER:
arch/x86/kvm/xen.c-1233- /*
--
tools/arch/x86/include/uapi/asm/kvm.h=668=struct kvm_xen_vcpu_attr {
--
tools/arch/x86/include/uapi/asm/kvm.h-702-#define KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID 0x6
tools/arch/x86/include/uapi/asm/kvm.h:703:#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
tools/arch/x86/include/uapi/asm/kvm.h-704-#define KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR 0x8
--
tools/testing/selftests/kvm/x86/xen_shinfo_test.c=434=int main(int argc, char *argv[])
--
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-577- struct kvm_xen_vcpu_attr tmr = {
tools/testing/selftests/kvm/x86/xen_shinfo_test.c:578: .type = KVM_XEN_VCPU_ATTR_TYPE_TIMER,
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-579- .u.timer.port = EVTCHN_TIMER,
--
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-792- memset(&tmr, 0, sizeof(tmr));
tools/testing/selftests/kvm/x86/xen_shinfo_test.c:793: tmr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-794- vcpu_ioctl(vcpu, KVM_XEN_VCPU_GET_ATTR, &tmr);
]
|
| 33/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 25686
output: 50
thoughts: 36
Thoughts: **My Thought Process Regarding `kvm_xen_vcpu_attr`**
Alright, so my initial impulse is to dive right into the heart of it and examine the `struct kvm_xen_vcpu_attr` definition. I'm looking for it specifically within `arch/x86/include/uapi/asm/kvm.h`. This is the foundational step, really. Before I can begin to understand *how* KVM is interacting with Xen at the vCPU attribute level, I need to see the raw data structure itself. What fields does it contain? What are their types? What kind of information is it designed to convey between the KVM hypervisor and the Xen guest? This is where the concrete details begin to emerge, and without this, any further speculation would be flying blind. It's all about getting my hands on the definitive definition to build my understanding upon.
|
| 34/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/include/uapi/asm/kvm.h Name:kvm_xen_vcpu_attr]
Results: map[SourceCode: 670: struct kvm_xen_vcpu_attr {
671: __u16 type;
672: __u16 pad[3];
673: union {
674: __u64 gpa;
675: #define KVM_XEN_INVALID_GPA ((__u64)-1)
676: __u64 hva;
677: __u64 pad[8];
678: struct {
679: __u64 state;
680: __u64 state_entry_time;
681: __u64 time_running;
682: __u64 time_runnable;
683: __u64 time_blocked;
684: __u64 time_offline;
685: } runstate;
686: __u32 vcpu_id;
687: struct {
688: __u32 port;
689: __u32 priority;
690: __u64 expires_ns;
691: } timer;
692: __u8 vector;
693: } u;
694: };
SourceFile:arch/x86/include/uapi/asm/kvm.h]
|
| 35/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 26132
output: 41
thoughts: 111
Thoughts: **My Thought Process Regarding KVM/Xen VCPU Timer Configuration**
Alright, so I'm looking at this `KVM_XEN_VCPU_ATTR_TYPE_TIMER` attribute, which I understand is represented by the hexadecimal value `0x7`. This tells me I'm specifically dealing with configuring a timer for a Xen virtual CPU within the KVM environment.
My next step is to set the `u.timer.port` field. The text suggests `1` as a valid port number. I recognize that this port is crucial for the communication channel or interrupt line associated with this timer event. It needs to be a port that the Xen hypervisor and guest can agree upon and utilize effectively.
The really interesting piece, and the one that immediately triggers a need for deeper investigation, is `u.timer.priority`. The value is given as `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL`. My immediate thought here is: "What *exactly* does this priority level signify?" I understand that interrupt routing and priority are fundamental to efficient interrupt handling and ensuring timely delivery of events. In a Xen environment, especially when interacting with KVM, the specific semantics of these priority levels are critical. I need to dig into the definition of `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL` to fully grasp its implications on how this timer interrupt will be prioritized and delivered to the virtual CPU. This is likely tied to the underlying Xen event channel mechanism and how KVM maps KVM interrupt routing attributes to Xen's own event handling and prioritization.
|
| 36/2 |
2026/08/12 13:19 |
tool |
grepper |
0m
Args: map[Expression:KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL PathPrefix:]
Results: map[Output:arch/x86/kvm/xen.c=109=void kvm_xen_inject_timer_irqs(struct kvm_vcpu *vcpu)
--
arch/x86/kvm/xen.c-116- e.port = vcpu->arch.xen.timer_virq;
arch/x86/kvm/xen.c:117: e.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
arch/x86/kvm/xen.c-118-
--
arch/x86/kvm/xen.c=126=static enum hrtimer_restart xen_timer_callback(struct hrtimer *timer)
--
arch/x86/kvm/xen.c-138- e.port = vcpu->arch.xen.timer_virq;
arch/x86/kvm/xen.c:139: e.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
arch/x86/kvm/xen.c-140-
--
arch/x86/kvm/xen.c=907=int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
--
arch/x86/kvm/xen.c-1118- if (data->u.timer.port &&
arch/x86/kvm/xen.c:1119: data->u.timer.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL) {
arch/x86/kvm/xen.c-1120- r = -EINVAL;
--
arch/x86/kvm/xen.c=1153=int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
--
arch/x86/kvm/xen.c-1247- data->u.timer.port = vcpu->arch.xen.timer_virq;
arch/x86/kvm/xen.c:1248: data->u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
arch/x86/kvm/xen.c-1249- data->u.timer.expires_ns = vcpu->arch.xen.timer_expires;
--
arch/x86/kvm/xen.c=1976=int kvm_xen_setup_evtchn(struct kvm *kvm,
--
arch/x86/kvm/xen.c-1997- /* We only support 2 level event channels for now */
arch/x86/kvm/xen.c:1998: if (ue->u.xen_evtchn.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL)
arch/x86/kvm/xen.c-1999- return -EINVAL;
--
arch/x86/kvm/xen.c=2026=int kvm_xen_hvm_evtchn_send(struct kvm *kvm, struct kvm_irq_routing_xen_evtchn *uxe)
--
arch/x86/kvm/xen.c-2034- /* We only support 2 level event channels for now */
arch/x86/kvm/xen.c:2035: if (uxe->priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL)
arch/x86/kvm/xen.c-2036- return -EINVAL;
--
arch/x86/kvm/xen.c=2073=static int kvm_xen_eventfd_update(struct kvm *kvm,
--
arch/x86/kvm/xen.c-2101- /* We only support 2 level event channels for now */
arch/x86/kvm/xen.c:2102: if (data->u.evtchn.deliver.port.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL)
arch/x86/kvm/xen.c-2103- goto out_unlock;
--
arch/x86/kvm/xen.c=2120=static int kvm_xen_eventfd_assign(struct kvm *kvm,
--
arch/x86/kvm/xen.c-2165- /* We only support 2 level event channels for now */
arch/x86/kvm/xen.c:2166: if (data->u.evtchn.deliver.port.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL)
arch/x86/kvm/xen.c-2167- goto out; /* -EINVAL; */
--
include/uapi/linux/kvm.h=1029=struct kvm_irq_routing_xen_evtchn {
--
include/uapi/linux/kvm.h-1034-
include/uapi/linux/kvm.h:1035:#define KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL ((__u32)(-1))
include/uapi/linux/kvm.h-1036-
--
tools/include/uapi/linux/kvm.h=1021=struct kvm_irq_routing_xen_evtchn {
--
tools/include/uapi/linux/kvm.h-1026-
tools/include/uapi/linux/kvm.h:1027:#define KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL ((__u32)(-1))
tools/include/uapi/linux/kvm.h-1028-
--
tools/testing/selftests/kvm/x86/xen_shinfo_test.c=434=int main(int argc, char *argv[])
--
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-558- irq_routes.entries[0].u.xen_evtchn.vcpu = vcpu->id;
tools/testing/selftests/kvm/x86/xen_shinfo_test.c:559: irq_routes.entries[0].u.xen_evtchn.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-560-
--
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-564- irq_routes.entries[1].u.xen_evtchn.vcpu = vcpu->id;
tools/testing/selftests/kvm/x86/xen_shinfo_test.c:565: irq_routes.entries[1].u.xen_evtchn.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-566-
--
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-579- .u.timer.port = EVTCHN_TIMER,
tools/testing/selftests/kvm/x86/xen_shinfo_test.c:580: .u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL,
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-581- .u.timer.expires_ns = 0
--
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-591- .u.evtchn.deliver.port.vcpu = vcpu->id + 1,
tools/testing/selftests/kvm/x86/xen_shinfo_test.c:592: .u.evtchn.deliver.port.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL,
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-593- };
--
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-739- e.vcpu = vcpu->id;
tools/testing/selftests/kvm/x86/xen_shinfo_test.c:740: e.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-741-
--
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-796- "Timer port not returned");
tools/testing/selftests/kvm/x86/xen_shinfo_test.c:797: TEST_ASSERT(tmr.u.timer.priority == KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL,
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-798- "Timer priority not returned");
--
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-902- .vcpu = vcpu->id,
tools/testing/selftests/kvm/x86/xen_shinfo_test.c:903: .priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL
tools/testing/selftests/kvm/x86/xen_shinfo_test.c-904- };
]
|
| 37/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 28837
output: 48
thoughts: 876
Thoughts: **My Thought Process on the KVM/Xen Bug**
It all started when I noticed that `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL` was evaluating to `((__u32)(-1))`. This seemed odd, and I decided to dive back into the bug trace to understand what was happening.
The trace pointed to a `BUG: sleeping function called from invalid context` at `kernel/locking/spinlock_rt.c:248`. The context was clearly atomic and interrupt-disabled (`in_atomic(): 1, irqs_disabled(): 1`), which immediately raised a red flag.
I then followed the call stack:
* The bug occurred within `rt_read_lock` at `kernel/locking/spinlock_rt.c:248`.
* This was called from `kvm_xen_set_evtchn_fast` in `arch/x86/kvm/xen.c`, specifically at line `1829`.
Looking at line `1829` in `kvm_xen_set_evtchn_fast`, I saw the offending line:
```c
read_lock_irqsave(&gpc->lock, flags);
```
My immediate thought was, "Is `read_lock_irqsave` on a `rwlock_t` a sleeping lock in PREEMPT_RT?" The answer, unfortunately, is yes. In a PREEMPT_RT environment, `read_lock_irqsave` applied to a `rwlock_t` effectively maps to `rt_read_lock`, which *can* sleep. Since the bug occurred in an atomic context (likely a hardirq callback due to the timer nature of Xen events), calling a sleeping lock there is a definite no-go.
The next critical question was: "How do I reproduce this?" I needed to trigger `kvm_xen_set_evtchn_fast` from an invalid context.
My initial thought was that it might require a fully set up Xen environment, including the `shinfo_cache` (the Xen shared info page). However, as I examined the code snippet more closely:
```c
read_lock_irqsave(&gpc->lock, flags);
if (!kvm_gpc_check(gpc, PAGE_SIZE))
goto out_rcu;
```
I realized something crucial: `read_lock_irqsave` is called *unconditionally*. Even if `kvm_gpc_check` fails, the lock is still acquired. This simplified things considerably. I didn't need to worry about the intricacies of the shared info page for the initial reproduction.
Therefore, the minimal steps to trigger this bug became clear:
1. Create a KVM virtual machine.
2. Enable Xen support (specifically, the `KVM_CAP_XEN_HVM` capability).
3. Create a virtual CPU for the VM.
4. Set a Xen timer using the `KVM_XEN_VCPU_SET_ATTR` ioctl with the `KVM_XEN_VCPU_ATTR_TYPE_TIMER` attribute, setting it to expire in the future.
5. Simply wait for that timer to fire, which should cause the KVM Xen event handler to be invoked, leading to the call to `kvm_xen_set_evtchn_fast` from an invalid context.
This realization about the unconditional lock acquisition was key to understanding the minimal reproduction path.
|
| 38/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/x86.c Name:kvm_vm_ioctl_enable_cap]
Results: map[SourceCode:3944: int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
3945: struct kvm_enable_cap *cap)
3946: {
3947: int r;
3948:
3949: if (cap->flags)
3950: return -EINVAL;
3951:
3952: switch (cap->cap) {
3953: case KVM_CAP_DISABLE_QUIRKS2:
3954: r = -EINVAL;
3955: if (cap->args[0] & ~kvm_caps.supported_quirks)
3956: break;
3957: fallthrough;
3958: case KVM_CAP_DISABLE_QUIRKS:
3959: mutex_lock(&kvm->lock);
3960: WRITE_ONCE(kvm->arch.disabled_quirks,
3961: kvm->arch.disabled_quirks | (cap->args[0] & kvm_caps.supported_quirks));
3962: mutex_unlock(&kvm->lock);
3963: r = 0;
3964: break;
3965: case KVM_CAP_SPLIT_IRQCHIP: {
3966: mutex_lock(&kvm->lock);
3967: r = -EINVAL;
3968: if (cap->args[0] > KVM_MAX_IRQ_ROUTES)
3969: goto split_irqchip_unlock;
3970: r = -EEXIST;
3971: if (irqchip_in_kernel(kvm))
3972: goto split_irqchip_unlock;
3973: if (kvm->created_vcpus)
3974: goto split_irqchip_unlock;
3975: /* Pairs with irqchip_in_kernel. */
3976: smp_wmb();
3977: kvm->arch.irqchip_mode = KVM_IRQCHIP_SPLIT;
3978: kvm->arch.nr_reserved_ioapic_pins = cap->args[0];
3979: kvm_clear_apicv_inhibit(kvm, APICV_INHIBIT_REASON_ABSENT);
3980: r = 0;
3981: split_irqchip_unlock:
3982: mutex_unlock(&kvm->lock);
3983: break;
3984: }
3985: case KVM_CAP_X2APIC_API:
3986: r = -EINVAL;
3987: if (cap->args[0] & ~KVM_X2APIC_API_VALID_FLAGS)
3988: break;
3989:
3990: if ((cap->args[0] & KVM_X2APIC_ENABLE_SUPPRESS_EOI_BROADCAST) &&
3991: (cap->args[0] & KVM_X2APIC_DISABLE_SUPPRESS_EOI_BROADCAST))
3992: break;
3993:
3994: if ((cap->args[0] & KVM_X2APIC_ENABLE_SUPPRESS_EOI_BROADCAST) &&
3995: !irqchip_split(kvm))
3996: break;
3997:
3998: if (cap->args[0] & KVM_X2APIC_API_USE_32BIT_IDS)
3999: kvm->arch.x2apic_format = true;
4000: if (cap->args[0] & KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK)
4001: kvm->arch.x2apic_broadcast_quirk_disabled = true;
4002:
4003: if (cap->args[0] & KVM_X2APIC_ENABLE_SUPPRESS_EOI_BROADCAST)
4004: kvm->arch.suppress_eoi_broadcast_mode = KVM_SUPPRESS_EOI_BROADCAST_ENABLED;
4005: if (cap->args[0] & KVM_X2APIC_DISABLE_SUPPRESS_EOI_BROADCAST)
4006: kvm->arch.suppress_eoi_broadcast_mode = KVM_SUPPRESS_EOI_BROADCAST_DISABLED;
4007:
4008: r = 0;
4009: break;
4010: case KVM_CAP_X86_DISABLE_EXITS:
4011: r = -EINVAL;
4012: if (cap->args[0] & ~kvm_get_allowed_disable_exits())
4013: break;
4014:
4015: mutex_lock(&kvm->lock);
4016: if (kvm->created_vcpus)
4017: goto disable_exits_unlock;
4018:
4019: #define SMT_RSB_MSG "This processor is affected by the Cross-Thread Return Predictions vulnerability. " \
4020: "KVM_CAP_X86_DISABLE_EXITS should only be used with SMT disabled or trusted guests."
4021:
4022: if (!mitigate_smt_rsb && boot_cpu_has_bug(X86_BUG_SMT_RSB) &&
4023: cpu_smt_possible() &&
4024: (cap->args[0] & ~(KVM_X86_DISABLE_EXITS_PAUSE |
4025: KVM_X86_DISABLE_EXITS_APERFMPERF)))
4026: pr_warn_once(SMT_RSB_MSG);
4027:
4028: kvm_disable_exits(kvm, cap->args[0]);
4029: r = 0;
4030: disable_exits_unlock:
4031: mutex_unlock(&kvm->lock);
4032: break;
4033: case KVM_CAP_MSR_PLATFORM_INFO:
4034: kvm->arch.guest_can_read_msr_platform_info = cap->args[0];
4035: r = 0;
4036: break;
4037: case KVM_CAP_EXCEPTION_PAYLOAD:
4038: kvm->arch.exception_payload_enabled = cap->args[0];
4039: r = 0;
4040: break;
4041: case KVM_CAP_X86_TRIPLE_FAULT_EVENT:
4042: kvm->arch.triple_fault_event = cap->args[0];
4043: r = 0;
4044: break;
4045: case KVM_CAP_X86_USER_SPACE_MSR:
4046: r = -EINVAL;
4047: if (cap->args[0] & ~KVM_MSR_EXIT_REASON_VALID_MASK)
4048: break;
4049: kvm->arch.user_space_msr_mask = cap->args[0];
4050: r = 0;
4051: break;
4052: case KVM_CAP_X86_BUS_LOCK_EXIT:
4053: r = -EINVAL;
4054: if (cap->args[0] & ~KVM_BUS_LOCK_DETECTION_VALID_MODE)
4055: break;
4056:
4057: if ((cap->args[0] & KVM_BUS_LOCK_DETECTION_OFF) &&
4058: (cap->args[0] & KVM_BUS_LOCK_DETECTION_EXIT))
4059: break;
4060:
4061: if (kvm_caps.has_bus_lock_exit &&
4062: cap->args[0] & KVM_BUS_LOCK_DETECTION_EXIT)
4063: kvm->arch.bus_lock_detection_enabled = true;
4064: r = 0;
4065: break;
4066: #ifdef CONFIG_X86_SGX_KVM
4067: case KVM_CAP_SGX_ATTRIBUTE: {
4068: unsigned long allowed_attributes = 0;
4069:
4070: r = sgx_set_attribute(&allowed_attributes, cap->args[0]);
4071: if (r)
4072: break;
4073:
4074: /* KVM only supports the PROVISIONKEY privileged attribute. */
4075: if ((allowed_attributes & SGX_ATTR_PROVISIONKEY) &&
4076: !(allowed_attributes & ~SGX_ATTR_PROVISIONKEY))
4077: kvm->arch.sgx_provisioning_allowed = true;
4078: else
4079: r = -EINVAL;
4080: break;
4081: }
4082: #endif
4083: case KVM_CAP_VM_COPY_ENC_CONTEXT_FROM:
4084: r = -EINVAL;
4085: if (!kvm_x86_ops.vm_copy_enc_context_from)
4086: break;
4087:
4088: r = kvm_x86_call(vm_copy_enc_context_from)(kvm, cap->args[0]);
4089: break;
4090: case KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM:
4091: r = -EINVAL;
4092: if (!kvm_x86_ops.vm_move_enc_context_from)
4093: break;
4094:
4095: r = kvm_x86_call(vm_move_enc_context_from)(kvm, cap->args[0]);
4096: break;
4097: case KVM_CAP_EXIT_HYPERCALL:
4098: if (cap->args[0] & ~KVM_EXIT_HYPERCALL_VALID_MASK) {
4099: r = -EINVAL;
4100: break;
4101: }
4102: kvm->arch.hypercall_exit_enabled = cap->args[0];
4103: r = 0;
4104: break;
4105: case KVM_CAP_EXIT_ON_EMULATION_FAILURE:
4106: r = -EINVAL;
4107: if (cap->args[0] & ~1)
4108: break;
4109: kvm->arch.exit_on_emulation_error = cap->args[0];
4110: r = 0;
4111: break;
4112: case KVM_CAP_PMU_CAPABILITY:
4113: r = -EINVAL;
4114: if (!enable_pmu || (cap->args[0] & ~KVM_CAP_PMU_VALID_MASK))
4115: break;
4116:
4117: if (kvm->arch.has_protected_pmu &&
4118: cap->args[0] != KVM_PMU_CAP_DISABLE)
4119: break;
4120:
4121: mutex_lock(&kvm->lock);
4122: if (!kvm->created_vcpus && !kvm->arch.created_mediated_pmu) {
4123: kvm->arch.enable_pmu = !(cap->args[0] & KVM_PMU_CAP_DISABLE);
4124: r = 0;
4125: }
4126: mutex_unlock(&kvm->lock);
4127: break;
4128: case KVM_CAP_MAX_VCPU_ID:
4129: r = -EINVAL;
4130: if (cap->args[0] > KVM_MAX_VCPU_IDS)
4131: break;
4132:
4133: mutex_lock(&kvm->lock);
4134: if (kvm->arch.bsp_vcpu_id > cap->args[0]) {
4135: ;
4136: } else if (kvm->arch.max_vcpu_ids == cap->args[0]) {
4137: r = 0;
4138: } else if (!kvm->arch.max_vcpu_ids) {
4139: kvm->arch.max_vcpu_ids = cap->args[0];
4140: r = 0;
4141: }
4142: mutex_unlock(&kvm->lock);
4143: break;
4144: case KVM_CAP_X86_NOTIFY_VMEXIT:
4145: r = -EINVAL;
4146: if ((u32)cap->args[0] & ~KVM_X86_NOTIFY_VMEXIT_VALID_BITS)
4147: break;
4148: if (!kvm_caps.has_notify_vmexit)
4149: break;
4150: if (!((u32)cap->args[0] & KVM_X86_NOTIFY_VMEXIT_ENABLED))
4151: break;
4152: mutex_lock(&kvm->lock);
4153: if (!kvm->created_vcpus) {
4154: kvm->arch.notify_window = cap->args[0] >> 32;
4155: kvm->arch.notify_vmexit_flags = (u32)cap->args[0];
4156: r = 0;
4157: }
4158: mutex_unlock(&kvm->lock);
4159: break;
4160: case KVM_CAP_VM_DISABLE_NX_HUGE_PAGES:
4161: r = -EINVAL;
4162:
4163: /*
4164: * Since the risk of disabling NX hugepages is a guest crashing
4165: * the system, ensure the userspace process has permission to
4166: * reboot the system.
4167: *
4168: * Note that unlike the reboot() syscall, the process must have
4169: * this capability in the root namespace because exposing
4170: * /dev/kvm into a container does not limit the scope of the
4171: * iTLB multihit bug to that container. In other words,
4172: * this must use capable(), not ns_capable().
4173: */
4174: if (!capable(CAP_SYS_BOOT)) {
4175: r = -EPERM;
4176: break;
4177: }
4178:
4179: if (cap->args[0])
4180: break;
4181:
4182: mutex_lock(&kvm->lock);
4183: if (!kvm->created_vcpus) {
4184: kvm->arch.disable_nx_huge_pages = true;
4185: r = 0;
4186: }
4187: mutex_unlock(&kvm->lock);
4188: break;
4189: case KVM_CAP_X86_APIC_BUS_CYCLES_NS: {
4190: u64 bus_cycle_ns = cap->args[0];
4191: u64 unused;
4192:
4193: /*
4194: * Guard against overflow in tmict_to_ns(). 128 is the highest
4195: * divide value that can be programmed in APIC_TDCR.
4196: */
4197: r = -EINVAL;
4198: if (!bus_cycle_ns ||
4199: check_mul_overflow((u64)U32_MAX * 128, bus_cycle_ns, &unused))
4200: break;
4201:
4202: r = 0;
4203: mutex_lock(&kvm->lock);
4204: if (!irqchip_in_kernel(kvm))
4205: r = -ENXIO;
4206: else if (kvm->created_vcpus)
4207: r = -EINVAL;
4208: else
4209: kvm->arch.apic_bus_cycle_ns = bus_cycle_ns;
4210: mutex_unlock(&kvm->lock);
4211: break;
4212: }
4213: default:
4214: r = -EINVAL;
4215: break;
4216: }
4217: return r;
4218: }
SourceFile:arch/x86/kvm/x86.c]
|
| 39/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 34413
output: 47
thoughts: 61
Thoughts: **My Thought Process Regarding KVM_CAP_XEN_HVM Handling**
I've just encountered a point of potential confusion regarding the `KVM_CAP_XEN_HVM` capability. My initial thought is to verify where this specific capability is processed within the KVM infrastructure. My current hypothesis, which I need to confirm, is that the `kvm_vm_ioctl_enable_cap` function, located in `virt/kvm/kvm_main.c`, is responsible for handling the enablement of `KVM_CAP_XEN_HVM`. To solidify this understanding, I intend to meticulously examine the source code of `kvm_vm_ioctl_enable_cap` to trace the execution path and confirm this assumption.
|
| 40/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:virt/kvm/kvm_main.c Name:kvm_vm_ioctl_enable_cap_generic]
Results: map[SourceCode:5033: static int kvm_vm_ioctl_enable_cap_generic(struct kvm *kvm,
5034: struct kvm_enable_cap *cap)
5035: {
5036: switch (cap->cap) {
5037: #ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
5038: case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2: {
5039: u64 allowed_options = KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE;
5040:
5041: if (cap->args[0] & KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE)
5042: allowed_options = KVM_DIRTY_LOG_MANUAL_CAPS;
5043:
5044: if (cap->flags || (cap->args[0] & ~allowed_options))
5045: return -EINVAL;
5046: kvm->manual_dirty_log_protect = cap->args[0];
5047: return 0;
5048: }
5049: #endif
5050: case KVM_CAP_HALT_POLL: {
5051: if (cap->flags || cap->args[0] != (unsigned int)cap->args[0])
5052: return -EINVAL;
5053:
5054: kvm->max_halt_poll_ns = cap->args[0];
5055:
5056: /*
5057: * Ensure kvm->override_halt_poll_ns does not become visible
5058: * before kvm->max_halt_poll_ns.
5059: *
5060: * Pairs with the smp_rmb() in kvm_vcpu_max_halt_poll_ns().
5061: */
5062: smp_wmb();
5063: kvm->override_halt_poll_ns = true;
5064:
5065: return 0;
5066: }
5067: case KVM_CAP_DIRTY_LOG_RING:
5068: case KVM_CAP_DIRTY_LOG_RING_ACQ_REL:
5069: if (!kvm_vm_ioctl_check_extension_generic(kvm, cap->cap))
5070: return -EINVAL;
5071:
5072: return kvm_vm_ioctl_enable_dirty_log_ring(kvm, cap->args[0]);
5073: case KVM_CAP_DIRTY_LOG_RING_WITH_BITMAP: {
5074: int r = -EINVAL;
5075:
5076: if (!IS_ENABLED(CONFIG_NEED_KVM_DIRTY_RING_WITH_BITMAP) ||
5077: !kvm->dirty_ring_size || cap->flags)
5078: return r;
5079:
5080: mutex_lock(&kvm->slots_lock);
5081:
5082: /*
5083: * For simplicity, allow enabling ring+bitmap if and only if
5084: * there are no memslots, e.g. to ensure all memslots allocate
5085: * a bitmap after the capability is enabled.
5086: */
5087: if (kvm_are_all_memslots_empty(kvm)) {
5088: kvm->dirty_ring_with_bitmap = true;
5089: r = 0;
5090: }
5091:
5092: mutex_unlock(&kvm->slots_lock);
5093:
5094: return r;
5095: }
5096: default:
5097: return kvm_vm_ioctl_enable_cap(kvm, cap);
5098: }
5099: }
SourceFile:virt/kvm/kvm_main.c]
|
| 41/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 35610
output: 39
thoughts: 18
Thoughts: **My Thought Process Regarding `KVM_CAP_XEN_HVM`**
Okay, so my immediate thought upon encountering the mention of `KVM_CAP_XEN_HVM` is a question that jumps right to the forefront of my mind: *where exactly is this specific capability being enabled or exposed?* It’s not just a passive observation; it's a targeted inquiry. I'm trying to pinpoint the precise location or mechanism within the KVM (Kernel-based Virtual Machine) infrastructure where this particular Xen HVM (Hardware Virtual Machine) capability is brought to light and made available.
This isn't about a general understanding of KVM or Xen. My expertise tells me that capabilities are often dynamically exposed or conditionally compiled based on various factors. Therefore, my focus immediately narrows to the *implementation details*. I'm thinking about:
* **Kernel Configuration:** Is `KVM_CAP_XEN_HVM` tied to a specific Kconfig option? If so, what is it, and what are the dependencies? Am I looking for a `CONFIG_KVM_XEN_HVM` flag or something similar?
* **Module Loading:** Is it a feature that's activated when a specific KVM module is loaded, or perhaps when the Xen hypervisor itself is detected and initialized by the kernel?
* **CPU Feature Detection:** It's possible that the enablement is contingent on the underlying CPU supporting certain virtualization extensions, specifically those relevant to Xen HVM. So, I'm considering whether there's a check for CPU flags like `VMX` (Intel VT-x) or `SVM` (AMD-V) in conjunction with Xen-specific bits.
* **KVM Internal Logic:** Within the KVM core itself, I'm hypothesizing about specific code paths or functions responsible for enumerating and exposing capabilities. I'm wondering if there's a `kvm_check_cap` or similar function where this particular capability is registered.
* **Xen Hypervisor Integration:** Given the name, the interaction with the Xen hypervisor is paramount. I'm questioning how KVM detects the presence of Xen and how it then signals its ability to leverage Xen's HVM capabilities. Is it through a direct communication channel, or a shared data structure?
Essentially, my mind is racing through the potential control flow and decision points within the Linux kernel's virtualization subsystem. I’m not just asking "is it there?" but rather "how does it *become* there, and under what conditions?" This is a practical, implementation-oriented question driven by the need to understand the operational footprint and dependencies of this feature.
|
| 42/2 |
2026/08/12 13:19 |
tool |
grepper |
0m
Args: map[Expression:KVM_CAP_XEN_HVM PathPrefix:arch/x86/kvm/]
Results: map[Output:arch/x86/kvm/x86.c=2203=int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
--
arch/x86/kvm/x86.c-2299-#ifdef CONFIG_KVM_XEN
arch/x86/kvm/x86.c:2300: case KVM_CAP_XEN_HVM:
arch/x86/kvm/x86.c-2301- r = KVM_XEN_HVM_CONFIG_HYPERCALL_MSR |
]
|
| 43/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 35813
output: 39
thoughts: 48
Thoughts: **My Thought Process Regarding Xen HVM Enablement in KVM**
Alright, so I just encountered a check for `KVM_CAP_XEN_HVM`. My immediate question is, "How do we actually *enable* this Xen HVM capability within KVM?" To get to the bottom of this, I'm diving into the kernel source, specifically `arch/x86/kvm/xen.c`. This is where I expect to find the implementation details and the logic that governs the activation of Xen HVM support. I'm anticipating tracing the code path that handles this capability, looking for conditional checks, configuration options, or specific Xen hypervisor interactions that lead to its enablement.
|
| 44/2 |
2026/08/12 13:19 |
tool |
grepper |
0m
Args: map[Expression:KVM_XEN_HVM_CONFIG PathPrefix:arch/x86/kvm/]
Results: map[Output:arch/x86/kvm/x86.c=1763=int kvm_guest_time_update(struct kvm_vcpu *v)
--
arch/x86/kvm/x86.c-1876- */
arch/x86/kvm/x86.c:1877: if (ka->xen.hvm_config.flags & KVM_XEN_HVM_CONFIG_PVCLOCK_TSC_UNSTABLE)
arch/x86/kvm/x86.c-1878- hv_clock.flags &= ~PVCLOCK_TSC_STABLE_BIT;
--
arch/x86/kvm/x86.c=2203=int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
--
arch/x86/kvm/x86.c-2300- case KVM_CAP_XEN_HVM:
arch/x86/kvm/x86.c:2301: r = KVM_XEN_HVM_CONFIG_HYPERCALL_MSR |
arch/x86/kvm/x86.c:2302: KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL |
arch/x86/kvm/x86.c:2303: KVM_XEN_HVM_CONFIG_SHARED_INFO |
arch/x86/kvm/x86.c:2304: KVM_XEN_HVM_CONFIG_EVTCHN_2LEVEL |
arch/x86/kvm/x86.c:2305: KVM_XEN_HVM_CONFIG_EVTCHN_SEND |
arch/x86/kvm/x86.c:2306: KVM_XEN_HVM_CONFIG_PVCLOCK_TSC_UNSTABLE |
arch/x86/kvm/x86.c:2307: KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA;
arch/x86/kvm/x86.c-2308- if (sched_info_on())
arch/x86/kvm/x86.c:2309: r |= KVM_XEN_HVM_CONFIG_RUNSTATE |
arch/x86/kvm/x86.c:2310: KVM_XEN_HVM_CONFIG_RUNSTATE_UPDATE_FLAG;
arch/x86/kvm/x86.c-2311- break;
--
arch/x86/kvm/x86.c=4374=int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
--
arch/x86/kvm/x86.c-4604-#ifdef CONFIG_KVM_XEN
arch/x86/kvm/x86.c:4605: case KVM_XEN_HVM_CONFIG: {
arch/x86/kvm/x86.c-4606- struct kvm_xen_hvm_config xhc;
--
arch/x86/kvm/xen.c=1365=int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc)
--
arch/x86/kvm/xen.c-1367- /* Only some feature flags need to be *enabled* by userspace */
arch/x86/kvm/xen.c:1368: u32 permitted_flags = KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL |
arch/x86/kvm/xen.c:1369: KVM_XEN_HVM_CONFIG_EVTCHN_SEND |
arch/x86/kvm/xen.c:1370: KVM_XEN_HVM_CONFIG_PVCLOCK_TSC_UNSTABLE;
arch/x86/kvm/xen.c-1371- u32 old_flags;
--
arch/x86/kvm/xen.c-1379- */
arch/x86/kvm/xen.c:1380: if ((xhc->flags & KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL) &&
arch/x86/kvm/xen.c-1381- (xhc->blob_addr_32 || xhc->blob_addr_64 ||
--
arch/x86/kvm/xen.c-1405-
arch/x86/kvm/xen.c:1406: if ((old_flags ^ xhc->flags) & KVM_XEN_HVM_CONFIG_PVCLOCK_TSC_UNSTABLE)
arch/x86/kvm/xen.c-1407- kvm_make_all_cpus_request(kvm, KVM_REQ_CLOCK_UPDATE);
--
arch/x86/kvm/xen.c=1474=static bool kvm_xen_schedop_poll(struct kvm_vcpu *vcpu, bool longmode,
--
arch/x86/kvm/xen.c-1482- if (!lapic_in_kernel(vcpu) ||
arch/x86/kvm/xen.c:1483: !(vcpu->kvm->arch.xen.hvm_config.flags & KVM_XEN_HVM_CONFIG_EVTCHN_SEND))
arch/x86/kvm/xen.c-1484- return false;
--
arch/x86/kvm/xen.h=75=static inline bool kvm_xen_hypercall_enabled(struct kvm *kvm)
--
arch/x86/kvm/xen.h-78- (kvm->arch.xen.hvm_config.flags &
arch/x86/kvm/xen.h:79: KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL);
arch/x86/kvm/xen.h-80-}
]
|
| 45/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 37455
output: 47
thoughts: 59
Thoughts: **My Thought Process on Xen and KVM Configuration**
Initially, my attention was drawn to the `KVM_XEN_HVM_CONFIG` ioctl, recognizing its role in configuring Xen environments. However, a critical question immediately arose: is this configuration actually necessary for our current use case? This led me to pause and consider if Xen even needs to be explicitly configured by KVM in the first place. To address this, I decided to investigate the `kvm_xen_vcpu_set_attr` function. My hypothesis is that if this function *itself* necessitates Xen being enabled, then the preceding `KVM_XEN_HVM_CONFIG` might be a prerequisite. Conversely, if `kvm_xen_vcpu_set_attr` can operate without Xen being pre-configured, it might suggest that the `KVM_XEN_HVM_CONFIG` ioctl is either optional or relevant only under specific, perhaps more advanced, Xen integration scenarios. This line of inquiry is crucial for understanding the precise dependencies and activation pathways for Xen features within KVM.
|
| 46/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c Name:kvm_xen_vcpu_set_attr]
Results: map[SourceCode: 907: int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
908: {
909: int idx, r = -ENOENT;
910:
911: mutex_lock(&vcpu->kvm->arch.xen.xen_lock);
912: idx = srcu_read_lock(&vcpu->kvm->srcu);
913:
914: switch (data->type) {
915: case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO:
916: case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA:
917: /* No compat necessary here. */
918: BUILD_BUG_ON(sizeof(struct vcpu_info) !=
919: sizeof(struct compat_vcpu_info));
920: BUILD_BUG_ON(offsetof(struct vcpu_info, time) !=
921: offsetof(struct compat_vcpu_info, time));
922:
923: if (data->type == KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO) {
924: if (data->u.gpa == KVM_XEN_INVALID_GPA) {
925: kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
926: r = 0;
927: break;
928: }
929:
930: r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_info_cache,
931: data->u.gpa, sizeof(struct vcpu_info));
932: } else {
933: if (data->u.hva == 0) {
934: kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
935: r = 0;
936: break;
937: }
938:
939: r = kvm_gpc_activate_hva(&vcpu->arch.xen.vcpu_info_cache,
940: data->u.hva, sizeof(struct vcpu_info));
941: }
942:
943: if (!r)
944: kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
945:
946: break;
947:
948: case KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO:
949: if (data->u.gpa == KVM_XEN_INVALID_GPA) {
950: kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_time_info_cache);
951: r = 0;
952: break;
953: }
954:
955: r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_time_info_cache,
956: data->u.gpa,
957: sizeof(struct pvclock_vcpu_time_info));
958: if (!r)
959: kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
960: break;
961:
962: case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADDR: {
963: size_t sz, sz1, sz2;
964:
965: if (!sched_info_on()) {
966: r = -EOPNOTSUPP;
967: break;
968: }
969: if (data->u.gpa == KVM_XEN_INVALID_GPA) {
970: r = 0;
971: deactivate_out:
972: kvm_gpc_deactivate(&vcpu->arch.xen.runstate_cache);
973: kvm_gpc_deactivate(&vcpu->arch.xen.runstate2_cache);
974: break;
975: }
976:
977: /*
978: * If the guest switches to 64-bit mode after setting the runstate
979: * address, that's actually OK. kvm_xen_update_runstate_guest()
980: * will cope.
981: */
982: if (IS_ENABLED(CONFIG_64BIT) && vcpu->kvm->arch.xen.long_mode)
983: sz = sizeof(struct vcpu_runstate_info);
984: else
985: sz = sizeof(struct compat_vcpu_runstate_info);
986:
987: /* How much fits in the (first) page? */
988: sz1 = PAGE_SIZE - (data->u.gpa & ~PAGE_MASK);
989: r = kvm_gpc_activate(&vcpu->arch.xen.runstate_cache,
990: data->u.gpa, sz1);
991: if (r)
992: goto deactivate_out;
993:
994: /* Either map the second page, or deactivate the second GPC */
995: if (sz1 >= sz) {
996: kvm_gpc_deactivate(&vcpu->arch.xen.runstate2_cache);
997: } else {
998: sz2 = sz - sz1;
999: BUG_ON((data->u.gpa + sz1) & ~PAGE_MASK);
1000: r = kvm_gpc_activate(&vcpu->arch.xen.runstate2_cache,
1001: data->u.gpa + sz1, sz2);
1002: if (r)
1003: goto deactivate_out;
1004: }
1005:
1006: kvm_xen_update_runstate_guest(vcpu, false);
1007: break;
1008: }
1009: case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_CURRENT:
1010: if (!sched_info_on()) {
1011: r = -EOPNOTSUPP;
1012: break;
1013: }
1014: if (data->u.runstate.state > RUNSTATE_offline) {
1015: r = -EINVAL;
1016: break;
1017: }
1018:
1019: kvm_xen_update_runstate(vcpu, data->u.runstate.state);
1020: r = 0;
1021: break;
1022:
1023: case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_DATA:
1024: if (!sched_info_on()) {
1025: r = -EOPNOTSUPP;
1026: break;
1027: }
1028: if (data->u.runstate.state > RUNSTATE_offline) {
1029: r = -EINVAL;
1030: break;
1031: }
1032: if (data->u.runstate.state_entry_time !=
1033: (data->u.runstate.time_running +
1034: data->u.runstate.time_runnable +
1035: data->u.runstate.time_blocked +
1036: data->u.runstate.time_offline)) {
1037: r = -EINVAL;
1038: break;
1039: }
1040: if (get_kvmclock_ns(vcpu->kvm) <
1041: data->u.runstate.state_entry_time) {
1042: r = -EINVAL;
1043: break;
1044: }
1045:
1046: vcpu->arch.xen.current_runstate = data->u.runstate.state;
1047: vcpu->arch.xen.runstate_entry_time =
1048: data->u.runstate.state_entry_time;
1049: vcpu->arch.xen.runstate_times[RUNSTATE_running] =
1050: data->u.runstate.time_running;
1051: vcpu->arch.xen.runstate_times[RUNSTATE_runnable] =
1052: data->u.runstate.time_runnable;
1053: vcpu->arch.xen.runstate_times[RUNSTATE_blocked] =
1054: data->u.runstate.time_blocked;
1055: vcpu->arch.xen.runstate_times[RUNSTATE_offline] =
1056: data->u.runstate.time_offline;
1057: vcpu->arch.xen.last_steal = current->sched_info.run_delay;
1058: r = 0;
1059: break;
1060:
1061: case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST:
1062: if (!sched_info_on()) {
1063: r = -EOPNOTSUPP;
1064: break;
1065: }
1066: if (data->u.runstate.state > RUNSTATE_offline &&
1067: data->u.runstate.state != (u64)-1) {
1068: r = -EINVAL;
1069: break;
1070: }
1071: /* The adjustment must add up */
1072: if (data->u.runstate.state_entry_time !=
1073: (data->u.runstate.time_running +
1074: data->u.runstate.time_runnable +
1075: data->u.runstate.time_blocked +
1076: data->u.runstate.time_offline)) {
1077: r = -EINVAL;
1078: break;
1079: }
1080:
1081: if (get_kvmclock_ns(vcpu->kvm) <
1082: (vcpu->arch.xen.runstate_entry_time +
1083: data->u.runstate.state_entry_time)) {
1084: r = -EINVAL;
1085: break;
1086: }
1087:
1088: vcpu->arch.xen.runstate_entry_time +=
1089: data->u.runstate.state_entry_time;
1090: vcpu->arch.xen.runstate_times[RUNSTATE_running] +=
1091: data->u.runstate.time_running;
1092: vcpu->arch.xen.runstate_times[RUNSTATE_runnable] +=
1093: data->u.runstate.time_runnable;
1094: vcpu->arch.xen.runstate_times[RUNSTATE_blocked] +=
1095: data->u.runstate.time_blocked;
1096: vcpu->arch.xen.runstate_times[RUNSTATE_offline] +=
1097: data->u.runstate.time_offline;
1098:
1099: if (data->u.runstate.state <= RUNSTATE_offline)
1100: kvm_xen_update_runstate(vcpu, data->u.runstate.state);
1101: else if (vcpu->arch.xen.runstate_cache.active)
1102: kvm_xen_update_runstate_guest(vcpu, false);
1103: r = 0;
1104: break;
1105:
1106: case KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID:
1107: BUILD_BUG_ON(XEN_VCPU_ID_INVALID < KVM_MAX_VCPUS);
1108:
1109: if (data->u.vcpu_id >= KVM_MAX_VCPUS)
1110: r = -EINVAL;
1111: else {
1112: vcpu->arch.xen.vcpu_id = data->u.vcpu_id;
1113: r = 0;
1114: }
1115: break;
1116:
1117: case KVM_XEN_VCPU_ATTR_TYPE_TIMER:
1118: if (data->u.timer.port &&
1119: data->u.timer.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL) {
1120: r = -EINVAL;
1121: break;
1122: }
1123:
1124: /* Stop the timer (if it's running) before changing the vector */
1125: kvm_xen_stop_timer(vcpu);
1126: vcpu->arch.xen.timer_virq = data->u.timer.port;
1127:
1128: /* Start the timer if the new value has a valid vector+expiry. */
1129: if (data->u.timer.port && data->u.timer.expires_ns)
1130: kvm_xen_start_timer(vcpu, data->u.timer.expires_ns, false);
1131:
1132: r = 0;
1133: break;
1134:
1135: case KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR:
1136: if (data->u.vector && data->u.vector < 0x10)
1137: r = -EINVAL;
1138: else {
1139: vcpu->arch.xen.upcall_vector = data->u.vector;
1140: r = 0;
1141: }
1142: break;
1143:
1144: default:
1145: break;
1146: }
1147:
1148: srcu_read_unlock(&vcpu->kvm->srcu, idx);
1149: mutex_unlock(&vcpu->kvm->arch.xen.xen_lock);
1150: return r;
1151: }
SourceFile:arch/x86/kvm/xen.c]
|
| 47/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 41625
output: 47
thoughts: 63
Thoughts: **A Deep Dive into KVM Xen Attribute Handling**
As an expert deeply immersed in the intricacies of virtualization technologies, my initial thought process on encountering this particular code segment revolved around a perceived oversight: a potential lack of a fundamental check within `kvm_xen_vcpu_set_attr`. My immediate concern was whether this function, designed to manipulate Xen virtual CPU attributes, was being exposed or potentially invoked even when the Xen hypervisor environment itself hadn't been explicitly enabled. This, in my expert opinion, could lead to undefined behavior or unexpected errors if the underlying Xen-specific mechanisms weren't present or active.
This raised a subsequent, more pointed question in my mind: "Is the `KVM_XEN_VCPU_SET_ATTR` ioctl actually *available* or accessible without Xen being enabled within the KVM subsystem?" My experience suggests that such specific ioctls are typically guarded by conditional logic that ensures their functionality is only presented when the relevant architectural features are active. To resolve this uncertainty and to trace the intended control flow, my next logical step would be to meticulously examine the `kvm_arch_vcpu_ioctl` function. This is where the KVM architecture-specific handling of all VCPU ioctls is centralized, and I would expect to find the crucial branching logic that either allows or denies access to `KVM_XEN_VCPU_SET_ATTR` based on the KVM's configuration and the host's hypervisor capabilities. This investigation would be key to confirming whether my initial suspicion of a missing check was valid or if the architecture-level dispatch already provides the necessary guardrails.
|
| 48/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/x86.c Name:kvm_arch_vcpu_ioctl]
Results: map[SourceCode:3416: long kvm_arch_vcpu_ioctl(struct file *filp,
3417: unsigned int ioctl, unsigned long arg)
3418: {
3419: struct kvm_vcpu *vcpu = filp->private_data;
3420: void __user *argp = (void __user *)arg;
3421: int r;
3422: union {
3423: struct kvm_sregs2 *sregs2;
3424: struct kvm_lapic_state *lapic;
3425: struct kvm_xsave *xsave;
3426: struct kvm_xcrs *xcrs;
3427: void *buffer;
3428: } u;
3429:
3430: vcpu_load(vcpu);
3431:
3432: u.buffer = NULL;
3433: switch (ioctl) {
3434: case KVM_GET_LAPIC: {
3435: r = -EINVAL;
3436: if (!lapic_in_kernel(vcpu))
3437: goto out;
3438: u.lapic = kzalloc_obj(struct kvm_lapic_state);
3439:
3440: r = -ENOMEM;
3441: if (!u.lapic)
3442: goto out;
3443: r = kvm_vcpu_ioctl_get_lapic(vcpu, u.lapic);
3444: if (r)
3445: goto out;
3446: r = -EFAULT;
3447: if (copy_to_user(argp, u.lapic, sizeof(struct kvm_lapic_state)))
3448: goto out;
3449: r = 0;
3450: break;
3451: }
3452: case KVM_SET_LAPIC: {
3453: r = -EINVAL;
3454: if (!lapic_in_kernel(vcpu))
3455: goto out;
3456: u.lapic = memdup_user(argp, sizeof(*u.lapic));
3457: if (IS_ERR(u.lapic)) {
3458: r = PTR_ERR(u.lapic);
3459: goto out_nofree;
3460: }
3461:
3462: r = kvm_vcpu_ioctl_set_lapic(vcpu, u.lapic);
3463: break;
3464: }
3465: case KVM_INTERRUPT: {
3466: struct kvm_interrupt irq;
3467:
3468: r = -EFAULT;
3469: if (copy_from_user(&irq, argp, sizeof(irq)))
3470: goto out;
3471: r = kvm_vcpu_ioctl_interrupt(vcpu, &irq);
3472: break;
3473: }
3474: case KVM_NMI: {
3475: r = kvm_vcpu_ioctl_nmi(vcpu);
3476: break;
3477: }
3478: case KVM_SMI: {
3479: r = kvm_inject_smi(vcpu);
3480: break;
3481: }
3482: case KVM_SET_CPUID: {
3483: struct kvm_cpuid __user *cpuid_arg = argp;
3484: struct kvm_cpuid cpuid;
3485:
3486: r = -EFAULT;
3487: if (copy_from_user(&cpuid, cpuid_arg, sizeof(cpuid)))
3488: goto out;
3489: r = kvm_vcpu_ioctl_set_cpuid(vcpu, &cpuid, cpuid_arg->entries);
3490: break;
3491: }
3492: case KVM_SET_CPUID2: {
3493: struct kvm_cpuid2 __user *cpuid_arg = argp;
3494: struct kvm_cpuid2 cpuid;
3495:
3496: r = -EFAULT;
3497: if (copy_from_user(&cpuid, cpuid_arg, sizeof(cpuid)))
3498: goto out;
3499: r = kvm_vcpu_ioctl_set_cpuid2(vcpu, &cpuid,
3500: cpuid_arg->entries);
3501: break;
3502: }
3503: case KVM_GET_CPUID2: {
3504: struct kvm_cpuid2 __user *cpuid_arg = argp;
3505: struct kvm_cpuid2 cpuid;
3506:
3507: r = -EFAULT;
3508: if (copy_from_user(&cpuid, cpuid_arg, sizeof(cpuid)))
3509: goto out;
3510: r = kvm_vcpu_ioctl_get_cpuid2(vcpu, &cpuid,
3511: cpuid_arg->entries);
3512: if (r)
3513: goto out;
3514: r = -EFAULT;
3515: if (copy_to_user(cpuid_arg, &cpuid, sizeof(cpuid)))
3516: goto out;
3517: r = 0;
3518: break;
3519: }
3520: case KVM_GET_MSRS:
3521: r = kvm_get_msrs(vcpu, argp);
3522: break;
3523: case KVM_SET_MSRS:
3524: r = kvm_set_msrs(vcpu, argp);
3525: break;
3526: case KVM_GET_ONE_REG:
3527: case KVM_SET_ONE_REG:
3528: r = kvm_get_set_one_reg(vcpu, ioctl, argp);
3529: break;
3530: case KVM_GET_REG_LIST:
3531: r = kvm_get_reg_list(vcpu, argp);
3532: break;
3533: case KVM_TPR_ACCESS_REPORTING: {
3534: struct kvm_tpr_access_ctl tac;
3535:
3536: r = -EFAULT;
3537: if (copy_from_user(&tac, argp, sizeof(tac)))
3538: goto out;
3539: r = vcpu_ioctl_tpr_access_reporting(vcpu, &tac);
3540: if (r)
3541: goto out;
3542: r = -EFAULT;
3543: if (copy_to_user(argp, &tac, sizeof(tac)))
3544: goto out;
3545: r = 0;
3546: break;
3547: };
3548: case KVM_SET_VAPIC_ADDR: {
3549: struct kvm_vapic_addr va;
3550: int idx;
3551:
3552: r = -EINVAL;
3553: if (!lapic_in_kernel(vcpu))
3554: goto out;
3555: r = -EFAULT;
3556: if (copy_from_user(&va, argp, sizeof(va)))
3557: goto out;
3558: idx = srcu_read_lock(&vcpu->kvm->srcu);
3559: r = kvm_lapic_set_vapic_addr(vcpu, va.vapic_addr);
3560: srcu_read_unlock(&vcpu->kvm->srcu, idx);
3561: break;
3562: }
3563: case KVM_X86_SETUP_MCE: {
3564: u64 mcg_cap;
3565:
3566: r = -EFAULT;
3567: if (copy_from_user(&mcg_cap, argp, sizeof(mcg_cap)))
3568: goto out;
3569: r = kvm_vcpu_ioctl_x86_setup_mce(vcpu, mcg_cap);
3570: break;
3571: }
3572: case KVM_X86_SET_MCE: {
3573: struct kvm_x86_mce mce;
3574:
3575: r = -EFAULT;
3576: if (copy_from_user(&mce, argp, sizeof(mce)))
3577: goto out;
3578: r = kvm_vcpu_ioctl_x86_set_mce(vcpu, &mce);
3579: break;
3580: }
3581: case KVM_GET_VCPU_EVENTS: {
3582: struct kvm_vcpu_events events;
3583:
3584: kvm_vcpu_ioctl_x86_get_vcpu_events(vcpu, &events);
3585:
3586: r = -EFAULT;
3587: if (copy_to_user(argp, &events, sizeof(struct kvm_vcpu_events)))
3588: break;
3589: r = 0;
3590: break;
3591: }
3592: case KVM_SET_VCPU_EVENTS: {
3593: struct kvm_vcpu_events events;
3594:
3595: r = -EFAULT;
3596: if (copy_from_user(&events, argp, sizeof(struct kvm_vcpu_events)))
3597: break;
3598:
3599: kvm_vcpu_srcu_read_lock(vcpu);
3600: r = kvm_vcpu_ioctl_x86_set_vcpu_events(vcpu, &events);
3601: kvm_vcpu_srcu_read_unlock(vcpu);
3602: break;
3603: }
3604: case KVM_GET_DEBUGREGS: {
3605: struct kvm_debugregs dbgregs;
3606:
3607: r = kvm_vcpu_ioctl_x86_get_debugregs(vcpu, &dbgregs);
3608: if (r < 0)
3609: break;
3610:
3611: r = -EFAULT;
3612: if (copy_to_user(argp, &dbgregs,
3613: sizeof(struct kvm_debugregs)))
3614: break;
3615: r = 0;
3616: break;
3617: }
3618: case KVM_SET_DEBUGREGS: {
3619: struct kvm_debugregs dbgregs;
3620:
3621: r = -EFAULT;
3622: if (copy_from_user(&dbgregs, argp,
3623: sizeof(struct kvm_debugregs)))
3624: break;
3625:
3626: r = kvm_vcpu_ioctl_x86_set_debugregs(vcpu, &dbgregs);
3627: break;
3628: }
3629: case KVM_GET_XSAVE: {
3630: r = -EINVAL;
3631: if (vcpu->arch.guest_fpu.uabi_size > sizeof(struct kvm_xsave))
3632: break;
3633:
3634: u.xsave = kzalloc_obj(struct kvm_xsave);
3635: r = -ENOMEM;
3636: if (!u.xsave)
3637: break;
3638:
3639: r = kvm_vcpu_ioctl_x86_get_xsave(vcpu, u.xsave);
3640: if (r < 0)
3641: break;
3642:
3643: r = -EFAULT;
3644: if (copy_to_user(argp, u.xsave, sizeof(struct kvm_xsave)))
3645: break;
3646: r = 0;
3647: break;
3648: }
3649: case KVM_SET_XSAVE: {
3650: int size = vcpu->arch.guest_fpu.uabi_size;
3651:
3652: u.xsave = memdup_user(argp, size);
3653: if (IS_ERR(u.xsave)) {
3654: r = PTR_ERR(u.xsave);
3655: goto out_nofree;
3656: }
3657:
3658: r = kvm_vcpu_ioctl_x86_set_xsave(vcpu, u.xsave);
3659: break;
3660: }
3661:
3662: case KVM_GET_XSAVE2: {
3663: int size = vcpu->arch.guest_fpu.uabi_size;
3664:
3665: u.xsave = kzalloc(size, GFP_KERNEL);
3666: r = -ENOMEM;
3667: if (!u.xsave)
3668: break;
3669:
3670: r = kvm_vcpu_ioctl_x86_get_xsave2(vcpu, u.buffer, size);
3671: if (r < 0)
3672: break;
3673:
3674: r = -EFAULT;
3675: if (copy_to_user(argp, u.xsave, size))
3676: break;
3677:
3678: r = 0;
3679: break;
3680: }
3681:
3682: case KVM_GET_XCRS: {
3683: u.xcrs = kzalloc_obj(struct kvm_xcrs);
3684: r = -ENOMEM;
3685: if (!u.xcrs)
3686: break;
3687:
3688: r = kvm_vcpu_ioctl_x86_get_xcrs(vcpu, u.xcrs);
3689: if (r < 0)
3690: break;
3691:
3692: r = -EFAULT;
3693: if (copy_to_user(argp, u.xcrs,
3694: sizeof(struct kvm_xcrs)))
3695: break;
3696: r = 0;
3697: break;
3698: }
3699: case KVM_SET_XCRS: {
3700: u.xcrs = memdup_user(argp, sizeof(*u.xcrs));
3701: if (IS_ERR(u.xcrs)) {
3702: r = PTR_ERR(u.xcrs);
3703: goto out_nofree;
3704: }
3705:
3706: r = kvm_vcpu_ioctl_x86_set_xcrs(vcpu, u.xcrs);
3707: break;
3708: }
3709: case KVM_SET_TSC_KHZ: {
3710: u32 user_tsc_khz;
3711:
3712: r = -EINVAL;
3713:
3714: if (vcpu->arch.guest_tsc_protected)
3715: goto out;
3716:
3717: user_tsc_khz = (u32)arg;
3718:
3719: if (kvm_caps.has_tsc_control &&
3720: user_tsc_khz >= kvm_caps.max_guest_tsc_khz)
3721: goto out;
3722:
3723: if (user_tsc_khz == 0)
3724: user_tsc_khz = tsc_khz;
3725:
3726: if (!kvm_set_tsc_khz(vcpu, user_tsc_khz))
3727: r = 0;
3728:
3729: goto out;
3730: }
3731: case KVM_GET_TSC_KHZ: {
3732: r = vcpu->arch.virtual_tsc_khz;
3733: goto out;
3734: }
3735: case KVM_KVMCLOCK_CTRL: {
3736: r = kvm_set_guest_paused(vcpu);
3737: goto out;
3738: }
3739: case KVM_ENABLE_CAP: {
3740: struct kvm_enable_cap cap;
3741:
3742: r = -EFAULT;
3743: if (copy_from_user(&cap, argp, sizeof(cap)))
3744: goto out;
3745: r = kvm_vcpu_ioctl_enable_cap(vcpu, &cap);
3746: break;
3747: }
3748: case KVM_GET_NESTED_STATE: {
3749: struct kvm_nested_state __user *user_kvm_nested_state = argp;
3750: u32 user_data_size;
3751:
3752: r = -EINVAL;
3753: if (!kvm_nested_ops.enabled)
3754: break;
3755:
3756: BUILD_BUG_ON(sizeof(user_data_size) != sizeof(user_kvm_nested_state->size));
3757: r = -EFAULT;
3758: if (get_user(user_data_size, &user_kvm_nested_state->size))
3759: break;
3760:
3761: r = kvm_nested_call(get_state)(vcpu, user_kvm_nested_state, user_data_size);
3762: if (r < 0)
3763: break;
3764:
3765: if (r > user_data_size) {
3766: if (put_user(r, &user_kvm_nested_state->size))
3767: r = -EFAULT;
3768: else
3769: r = -E2BIG;
3770: break;
3771: }
3772:
3773: r = 0;
3774: break;
3775: }
3776: case KVM_SET_NESTED_STATE: {
3777: struct kvm_nested_state __user *user_kvm_nested_state = argp;
3778: struct kvm_nested_state kvm_state;
3779: int idx;
3780:
3781: r = -EINVAL;
3782: if (!kvm_nested_ops.enabled)
3783: break;
3784:
3785: r = -EFAULT;
3786: if (copy_from_user(&kvm_state, user_kvm_nested_state, sizeof(kvm_state)))
3787: break;
3788:
3789: r = -EINVAL;
3790: if (kvm_state.size < sizeof(kvm_state))
3791: break;
3792:
3793: if (kvm_state.flags &
3794: ~(KVM_STATE_NESTED_RUN_PENDING | KVM_STATE_NESTED_GUEST_MODE
3795: | KVM_STATE_NESTED_EVMCS | KVM_STATE_NESTED_MTF_PENDING
3796: | KVM_STATE_NESTED_GIF_SET))
3797: break;
3798:
3799: /* nested_run_pending implies guest_mode. */
3800: if ((kvm_state.flags & KVM_STATE_NESTED_RUN_PENDING)
3801: && !(kvm_state.flags & KVM_STATE_NESTED_GUEST_MODE))
3802: break;
3803:
3804: idx = srcu_read_lock(&vcpu->kvm->srcu);
3805: r = kvm_nested_call(set_state)(vcpu, user_kvm_nested_state, &kvm_state);
3806: srcu_read_unlock(&vcpu->kvm->srcu, idx);
3807: break;
3808: }
3809: #ifdef CONFIG_KVM_HYPERV
3810: case KVM_GET_SUPPORTED_HV_CPUID:
3811: r = kvm_ioctl_get_supported_hv_cpuid(vcpu, argp);
3812: break;
3813: #endif
3814: #ifdef CONFIG_KVM_XEN
3815: case KVM_XEN_VCPU_GET_ATTR: {
3816: struct kvm_xen_vcpu_attr xva;
3817:
3818: r = -EFAULT;
3819: if (copy_from_user(&xva, argp, sizeof(xva)))
3820: goto out;
3821: r = kvm_xen_vcpu_get_attr(vcpu, &xva);
3822: if (!r && copy_to_user(argp, &xva, sizeof(xva)))
3823: r = -EFAULT;
3824: break;
3825: }
3826: case KVM_XEN_VCPU_SET_ATTR: {
3827: struct kvm_xen_vcpu_attr xva;
3828:
3829: r = -EFAULT;
3830: if (copy_from_user(&xva, argp, sizeof(xva)))
3831: goto out;
3832: r = kvm_xen_vcpu_set_attr(vcpu, &xva);
3833: break;
3834: }
3835: #endif
3836: case KVM_GET_SREGS2: {
3837: r = -EINVAL;
3838: if (vcpu->kvm->arch.has_protected_state &&
3839: vcpu->arch.guest_state_protected)
3840: goto out;
3841:
3842: u.sregs2 = kzalloc_obj(struct kvm_sregs2);
3843: r = -ENOMEM;
3844: if (!u.sregs2)
3845: goto out;
3846: kvm_vcpu_ioctl_x86_get_sregs2(vcpu, u.sregs2);
3847: r = -EFAULT;
3848: if (copy_to_user(argp, u.sregs2, sizeof(struct kvm_sregs2)))
3849: goto out;
3850: r = 0;
3851: break;
3852: }
3853: case KVM_SET_SREGS2: {
3854: r = -EINVAL;
3855: if (vcpu->kvm->arch.has_protected_state &&
3856: vcpu->arch.guest_state_protected)
3857: goto out;
3858:
3859: u.sregs2 = memdup_user(argp, sizeof(struct kvm_sregs2));
3860: if (IS_ERR(u.sregs2)) {
3861: r = PTR_ERR(u.sregs2);
3862: u.sregs2 = NULL;
3863: goto out;
3864: }
3865: r = kvm_vcpu_ioctl_x86_set_sregs2(vcpu, u.sregs2);
3866: break;
3867: }
3868: case KVM_HAS_DEVICE_ATTR:
3869: case KVM_GET_DEVICE_ATTR:
3870: case KVM_SET_DEVICE_ATTR:
3871: r = kvm_vcpu_ioctl_device_attr(vcpu, ioctl, argp);
3872: break;
3873: case KVM_MEMORY_ENCRYPT_OP:
3874: r = -ENOTTY;
3875: if (!kvm_x86_ops.vcpu_mem_enc_ioctl)
3876: goto out;
3877: r = kvm_x86_ops.vcpu_mem_enc_ioctl(vcpu, argp);
3878: break;
3879: default:
3880: r = -EINVAL;
3881: }
3882: out:
3883: kfree(u.buffer);
3884: out_nofree:
3885: vcpu_put(vcpu);
3886: return r;
3887: }
SourceFile:arch/x86/kvm/x86.c]
|
| 49/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 48959
output: 44
thoughts: 551
Thoughts: **My Thought Process Regarding KVM_XEN_VCPU_SET_ATTR and the PREEMPT_RT Bug**
Okay, so I've been digging into the `KVM_XEN_VCPU_SET_ATTR` ioctl, and it seems like it's unconditionally available as long as `CONFIG_KVM_XEN` is enabled. This is interesting because it means I don't even need to have Xen explicitly enabled on the VM to potentially use this functionality.
Now, my immediate next step was to trace what happens when `KVM_XEN_VCPU_SET_ATTR` is called. I noticed it calls `kvm_xen_start_timer`. This led me to examine the code snippet provided for the timer attribute handling:
```c
case KVM_XEN_VCPU_ATTR_TYPE_TIMER:
if (data->u.timer.port &&
data->u.timer.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL) {
r = -EINVAL;
break;
}
/* Stop the timer (if it's running) before changing the vector */
kvm_xen_stop_timer(vcpu);
vcpu->arch.xen.timer_virq = data->u.timer.port;
/* Start the timer if the new value has a valid vector+expiry. */
if (data->u.timer.port && data->u.timer.expires_ns)
kvm_xen_start_timer(vcpu, data->u.timer.expires_ns, false);
r = 0;
break;
```
I specifically looked at the conditions under which `kvm_xen_start_timer` would be invoked. If I were to set `data->u.timer.port = 1`, `data->u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL`, and `data->u.timer.expires_ns = 10,000,000` (which translates to 10ms), it would indeed trigger `kvm_xen_start_timer`.
What happens next is crucial: `kvm_xen_start_timer` initiates an hrtimer. When this hrtimer fires, it calls `xen_timer_callback`. Following the execution path, `xen_timer_callback` then calls `kvm_xen_set_evtchn_fast`.
And this is where things get really interesting and point towards the PREEMPT_RT bug. `kvm_xen_set_evtchn_fast` acquires a read lock using `read_lock_irqsave(&gpc->lock, flags)`. This lock acquisition, in the context of PREEMPT_RT, is the problematic operation.
However, before I fully commit to that conclusion, a nagging question arises: Is the `gpc` pointer, which is accessed within `kvm_xen_set_evtchn_fast` as `gpc = &kvm->arch.xen.shinfo_cache;`, actually initialized? I need to go back and verify if `gpc` is properly set up, and the logical place to check this would be within the `kvm_xen_init_vm` function. This initialization step is critical for ensuring that subsequent operations on `gpc` don't result in dereferencing a null or uninitialized pointer, which could lead to unpredictable behavior, especially when combined with the locking mechanisms in PREEMPT_RT.
|
| 50/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c Name:kvm_xen_init_vm]
Results: map[SourceCode:2335: void kvm_xen_init_vm(struct kvm *kvm)
2336: {
2337: mutex_init(&kvm->arch.xen.xen_lock);
2338: idr_init(&kvm->arch.xen.evtchn_ports);
2339: kvm_gpc_init(&kvm->arch.xen.shinfo_cache, kvm);
2340: }
SourceFile:arch/x86/kvm/xen.c]
|
| 51/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 49685
output: 43
thoughts: 648
Thoughts: **My Thought Process Regarding KVM and Xen Integration**
Right, I was just digging into the KVM architecture, specifically how it handles Xen integration, and I've confirmed a crucial detail: the `kvm_gpc_init` function is indeed called. My trace shows it being invoked within `kvm_xen_init_vm`, which itself is a part of the broader `kvm_arch_init_vm` initialization sequence. This is important because it directly implies that the `gpc->lock` structure, which is fundamental for synchronization, gets properly initialized. So, from that perspective, I'm satisfied that the basic locking mechanism for Xen-related guest processor controls is in place.
However, as always, I'm not going to stop there. I need to be absolutely certain that everything else is covered. My next step is to really stress-test this initialization by attempting to reproduce a specific scenario. I've drafted a small C program to do just that. The idea is to set up a KVM VM and VCPU, and then utilize the `KVM_XEN_VCPU_ATTR_TYPE_TIMER` attribute to configure a Xen event channel timer. I'm setting the port to 1, the priority to `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL` (a constant I found, representing a specific priority level), and an expiration time of one second in the future. After issuing the `KVM_XEN_VCPU_SET_ATTR` ioctl, I'll introduce a two-second sleep to give the timer ample time to expire.
Now, while I'm looking at this code, a question pops into my head. I know I'm using `KVM_XEN_VCPU_SET_ATTR`, but I need to be sure I've got the correct ioctl *number* for it. My next immediate task is to go and find the exact numerical value for `KVM_XEN_VCPU_SET_ATTR` to ensure my test case is robust and accurate.
|
| 52/2 |
2026/08/12 13:19 |
tool |
grepper |
0m
Args: map[Expression:KVM_XEN_VCPU_SET_ATTR PathPrefix:include/uapi/linux/kvm.h]
Results: map[Output:include/uapi/linux/kvm.h=1442=struct kvm_enc_region {
--
include/uapi/linux/kvm.h-1484-#define KVM_XEN_VCPU_GET_ATTR _IOWR(KVMIO, 0xca, struct kvm_xen_vcpu_attr)
include/uapi/linux/kvm.h:1485:#define KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct kvm_xen_vcpu_attr)
include/uapi/linux/kvm.h-1486-
]
|
| 53/2 |
2026/08/12 13:19 |
llm |
initial-researcher |
0m
Model:
Tokens:
input: 50531
output: 45
thoughts: 841
Thoughts: **My Thought Process on the Xen Timer Bug**
Okay, let's walk through this. My immediate thought is about where `struct kvm_xen_vcpu_attr` is defined. I know it's in `arch/x86/include/uapi/asm/kvm.h`. So, to use it, I'll need to include `<linux/kvm.h>` and `<asm/kvm.h>`. A quick mental check confirms that `<linux/kvm.h>` already pulls in `<asm/kvm.h>`, so I'm good there. Then I need to make sure `KVM_XEN_VCPU_ATTR_TYPE_TIMER` is also defined in `<asm/kvm.h>`, which it is.
Next, I'm considering the `expires_ns` field. The documentation says it's the absolute time in guest KVM clock. If I set it to, say, 1,000,000,000 (which is one second), is that guaranteed to be in the future? I recall that `get_kvmclock_ns` starts from zero when the VM is created. So, yes, one second from the VM's epoch is definitely in the future. I'll quickly verify the KVM clock initialization. Ah, yes, `kvm->arch.kvmclock_offset = -get_kvmclock_base_ns();` and `data->clock = get_kvmclock_base_ns() + ka->kvmclock_offset;`. This confirms `get_kvmclock_ns` indeed starts at zero.
So, if `expires_ns` is set to 1,000,000,000, the `delta` calculation will be `1,000,000,000 - guest_now`. Since `guest_now` is likely very small (just a few milliseconds into the VM's lifetime), `delta` will be very close to one second. Then, when `hrtimer_start` is called with `ktime_add_ns(kernel_now, delta)`, the timer is effectively scheduled to fire about one second from now.
Here's where the critical part comes in: when this timer fires, it will execute in a hardirq context because it's `HRTIMER_MODE_ABS_HARD`. This will lead to `xen_timer_callback` being invoked. And that callback then calls `kvm_xen_set_evtchn_fast`. The problem arises when `kvm_xen_set_evtchn_fast` calls `read_lock_irqsave(&gpc->lock, flags)`. In a PREEMPT_RT environment, this `read_lock_irqsave` becomes a sleeping lock. And that's the bug – we're trying to acquire a sleeping lock in a hardirq context.
I should also double-check if there are any preconditions that need to be met for this to trigger. Does the VCPU need to be actively running? No, `hrtimer_start` is called regardless of the VCPU's running state. Does the VM need to have Xen enabled via `KVM_XEN_HVM_CONFIG`? Looking at the `kvm_xen_vcpu_set_attr` function again:
```c
case KVM_XEN_VCPU_ATTR_TYPE_TIMER:
if (data->u.timer.port &&
data->u.timer.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL) {
r = -EINVAL;
break;
}
/* Stop the timer (if it's running) before changing the vector */
kvm_xen_stop_timer(vcpu);
vcpu->arch.xen.timer_virq = data->u.timer.port;
/* Start the timer if the new value has a valid vector+expiry. */
if (data->u.timer.port && data->u.timer.expires_ns)
kvm_xen_start_timer(vcpu, data->u.timer.expires_ns, false);
r = 0;
break;
```
There are no explicit checks here for Xen being enabled. This means the `KVM_XEN_VCPU_ATTR_TYPE_TIMER` ioctl can be called even if Xen isn't fully configured.
Finally, I'm quickly thinking about the initialization of `xen_timer_callback`. I should check `kvm_xen_init_vcpu` to ensure that the relevant structures are set up correctly.
|
| 54/2 |
2026/08/12 13:19 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c Name:kvm_xen_init_vcpu]
Results: map[SourceCode:2307: void kvm_xen_init_vcpu(struct kvm_vcpu *vcpu)
2308: {
2309: vcpu->arch.xen.vcpu_id = XEN_VCPU_ID_INVALID;
2310: vcpu->arch.xen.poll_evtchn = 0;
2311:
2312: timer_setup(&vcpu->arch.xen.poll_timer, cancel_evtchn_poll, 0);
2313: hrtimer_setup(&vcpu->arch.xen.timer, xen_timer_callback, CLOCK_MONOTONIC,
2314: HRTIMER_MODE_ABS_HARD);
2315:
2316: kvm_gpc_init(&vcpu->arch.xen.runstate_cache, vcpu->kvm);
2317: kvm_gpc_init(&vcpu->arch.xen.runstate2_cache, vcpu->kvm);
2318: kvm_gpc_init(&vcpu->arch.xen.vcpu_info_cache, vcpu->kvm);
2319: kvm_gpc_init(&vcpu->arch.xen.vcpu_time_info_cache, vcpu->kvm);
2320: }
SourceFile:arch/x86/kvm/xen.c]
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llm |
initial-researcher |
0m
Model:
Tokens:
input: 51764
output: 67
thoughts: 42
Thoughts: **My Thought Process Regarding `kvm_xen_init_vcpu`**
Ah, I'm trying to pinpoint the exact moment `kvm_xen_init_vcpu` is invoked in the KVM Xen integration. My initial understanding is that this function is indeed called during the creation of a VCPU for a Xen guest. To solidify this, I need to perform a detailed verification of the call sites within the KVM Xen code. I'm not just taking it as gospel; I'm driven to trace the execution flow myself to confirm precisely where and when this initialization routine for Xen VCPUs is triggered.
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tool |
codesearch-find-references |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c IncludeSnippetLines:5 Name:kvm_xen_init_vcpu SourceTreePrefix:arch/x86/kvm/]
Results: map[References:[map[ReferenceKind:calls ReferencingEntityKind:function ReferencingEntityName:kvm_arch_vcpu_create SourceFile:arch/x86/kvm/x86.c SourceLine:9389 SourceSnippet:9384:
9385: r = kvm_x86_call(vcpu_create)(vcpu);
9386: if (r)
9387: goto free_guest_fpu;
9388:
9389: kvm_xen_init_vcpu(vcpu);
9390: vcpu_load(vcpu);
9391: kvm_vcpu_after_set_cpuid(vcpu);
9392: kvm_set_tsc_khz(vcpu, vcpu->kvm->arch.default_tsc_khz);
9393: kvm_vcpu_reset(vcpu, false);
9394: kvm_init_mmu(vcpu);
]] TruncatedOutput:false]
|
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llm |
initial-researcher |
0m
Model:
Tokens:
input: 52113
output: 42
thoughts: 228
Thoughts: **My Thought Process Regarding KVM Xen Event Channel Timer Configuration**
My immediate thought upon encountering the issue was to pinpoint the exact function responsible for creating the VCPU within KVM. I recalled that this is handled by `kvm_arch_vcpu_create`.
Following this, I considered the simplest possible sequence of actions to reproduce the observed behavior. This led me to the following reproduction steps:
1. First, I would need to open the `/dev/kvm` device.
2. Next, I'd create a virtual machine (VM).
3. Then, I would proceed to create a virtual CPU (VCPU) for that VM.
4. The crucial step involves interacting with the VCPU using the `KVM_XEN_VCPU_SET_ATTR` ioctl. Specifically, I'd set the attribute type to `KVM_XEN_VCPU_ATTR_TYPE_TIMER`, with a `port` value of `1`, a `priority` of `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL`, and an expiration time (`expires_ns`) of `100000000` (which translates to 100 milliseconds).
5. Finally, to confirm the timer functionality, I would introduce a short delay using a `sleep` call, allowing sufficient time for the timer to trigger.
After outlining these reproduction steps, a new question arose in my mind: I needed to investigate whether the `kvm_xen_set_evtchn_fast` function, which I suspect is involved in this timer setting, has any other prerequisites or dependencies that might be relevant. My initial check of the code snippet provided revealed a critical condition:
```c
if (xe->port >= max_evtchn_port(kvm))
return -EINVAL;
```
This snippet immediately prompts the question: "What exactly is the value returned by `max_evtchn_port(kvm)`?" Understanding this limit is essential for correctly configuring the event channel port and ensuring the operation doesn't fail due to an invalid port assignment.
|
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tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c Name:max_evtchn_port]
Results: map[SourceCode:1428: static inline int max_evtchn_port(struct kvm *kvm)
1429: {
1430: if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode)
1431: return EVTCHN_2L_NR_CHANNELS;
1432: else
1433: return COMPAT_EVTCHN_2L_NR_CHANNELS;
1434: }
SourceFile:arch/x86/kvm/xen.c]
|
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llm |
initial-researcher |
0m
Model:
Tokens:
input: 52522
output: 1370
thoughts: 6437
Thoughts: **The Path to Triggering a PREEMPT_RT Kernel Bug in KVM's Xen Timer Handling**
My investigation began with a peculiar observation about KVM's Xen event channel handling, specifically regarding the constants `EVTCHN_2L_NR_CHANNELS` and `COMPAT_EVTCHN_2L_NR_CHANNELS` both being 1024. This immediately suggested that `port = 1` would be a valid value in this context.
My focus then shifted to the `kvm_xen_set_evtchn_fast` function. I noticed it calls `srcu_read_lock(&kvm->srcu)`. My first thought was, "Is `kvm->srcu` properly initialized?" A quick mental check confirmed that it is, as it gets initialized during VM creation. Following the execution path, the next critical call is `read_lock_irqsave(&gpc->lock, flags)`. This particular line immediately raised a red flag for me. I recognized this as the specific lock acquisition that is known to trigger a bug in the PREEMPT_RT kernel.
To reliably demonstrate and reproduce this issue, I decided to construct a minimal C program. The core idea is to trigger the Xen timer mechanism in KVM. Here's how I envisioned the reproducer:
1. **Initialization:** I'll need to open the KVM device (`/dev/kvm`), then create a virtual machine (`KVM_CREATE_VM`), and subsequently a virtual CPU (`KVM_CREATE_VCPU`).
2. **Arming the Xen Timer:** The key step is to use the `KVM_XEN_VCPU_SET_ATTR` ioctl. I'll set the `type` to `KVM_XEN_VCPU_ATTR_TYPE_TIMER`. For the `timer` union member, I'll specify a `port` (which I've already reasoned should be valid, like `1`) and a `priority` (using `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL`). Crucially, I'll set `expires_ns` to a future timestamp, ensuring the timer is scheduled to fire asynchronously. I decided on 1 second (`1000000000ULL`) to be safe and guarantee it fires in the future, not synchronously during the ioctl call.
3. **Triggering the Bug:** After issuing the `KVM_XEN_VCPU_SET_ATTR` ioctl, I'll introduce a `sleep` call for a duration slightly longer than the timer's expiration (e.g., 2 seconds). This waiting period allows the system timer to expire. When the Xen timer fires, it's designed to do so in a hardirq context because it's armed with `HRTIMER_MODE_ABS_HARD`.
4. **The Crash:** The Xen timer's callback mechanism leads to `xen_timer_callback`, which in turn calls `kvm_xen_set_evtchn_fast`. As I identified earlier, this function attempts to acquire `gpc->lock` using `read_lock_irqsave`. In a PREEMPT_RT kernel, this operation, when applied to a `rwlock_t`, translates to `rt_read_lock`. This is a sleeping lock, and attempting to acquire a sleeping lock from a hardirq context is strictly forbidden and will cause the kernel to panic with a "sleeping function called from invalid context" bug.
I had to consider potential issues with older kernel headers. For instance, `KVM_XEN_VCPU_SET_ATTR` and `KVM_XEN_VCPU_ATTR_TYPE_TIMER`, along with the `struct kvm_xen_vcpu_attr`, might not be defined. To mitigate this, I planned to define these constants and the structure manually in my C code, aliasing the structure as `my_kvm_xen_vcpu_attr` and the ioctl macro as `MY_KVM_XEN_VCPU_SET_ATTR` to ensure compatibility.
A crucial check I performed was on the `kvm_xen_start_timer` function itself. My concern was whether it would correctly fall back to using `get_kvmclock_ns` if the Xen PV clocks weren't set up. Reviewing the code, I saw that if the PV clocks are inactive, the function indeed uses `get_kvmclock_ns(vcpu->kvm)` to determine the current guest time. `get_kvmclock_ns` returns the time elapsed since VM creation. This means that setting `expires_ns` to a value like 100ms or 1 second will result in a positive `delta` and the timer will be scheduled asynchronously, as intended for the bug trigger. My earlier decision to use 1 second for `expires_ns` and 2 seconds for `sleep` solidifies this asynchronous behavior.
Furthermore, I confirmed that the `KVM_XEN_VCPU_SET_ATTR` ioctl is available as long as `CONFIG_KVM_XEN` is enabled during kernel compilation. The function `kvm_xen_vcpu_set_attr` doesn't explicitly check if Xen is enabled for *this specific* ioctl, it merely sets up the timer.
Ultimately, my analysis led me to the conclusion that this bug is specific to PREEMPT_RT kernels due to the sleeping nature of `rt_read_lock` when acquiring `rwlock_t` in hardirq context. A standard kernel would handle `read_lock_irqsave` on a `rwlock_t` by simply disabling interrupts and taking the raw lock, which is permissible.
The resulting C code encapsulates this strategy: it's minimal, directly targets the Xen timer mechanism via the `KVM_XEN_VCPU_SET_ATTR` ioctl, and relies on the timer expiring in a hardirq context to trigger the PREEMPT_RT-specific `read_lock_irqsave` issue. It doesn't require memory mapping, VCPU execution, or complex Xen setup, making it a highly effective reproducer.
Here's the refined C code I arrived at:
```c
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
// Define necessary Xen timer related constants if not present in headers
#ifndef KVM_XEN_VCPU_ATTR_TYPE_TIMER
#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
#endif
#ifndef KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL
#define KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL ((uint32_t)(-1))
#endif
// Define the structure for Xen VCPU attributes if not present
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
// Define the KVM_XEN_VCPU_SET_ATTR ioctl if not present
// KVMIO is typically defined in <linux/kvm_host.h> which might not be installed
// so we define it based on the common value for KVMIO.
#ifndef KVMIO
#define KVMIO 0xAE
#endif
#ifndef KVM_XEN_VCPU_SET_ATTR
#define KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
#endif
int main(void)
{
int kvm_fd, vm_fd, vcpu_fd;
struct my_kvm_xen_vcpu_attr attr = {0};
// 1. Open KVM device
kvm_fd = open("/dev/kvm", O_RDWR);
if (kvm_fd < 0) {
perror("open /dev/kvm");
return 1;
}
// 2. Create a VM
vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0);
if (vm_fd < 0) {
perror("KVM_CREATE_VM");
return 1;
}
// 3. Create a VCPU
vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);
if (vcpu_fd < 0) {
perror("KVM_CREATE_VCPU");
return 1;
}
// 4. Configure the Xen timer attribute
attr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
attr.u.timer.port = 1; // A valid event channel port
attr.u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL; // Default priority
attr.u.timer.expires_ns = 1000000000ULL; // 1 second from now
// 5. Set the Xen timer attribute using the ioctl
if (ioctl(vcpu_fd, KVM_XEN_VCPU_SET_ATTR, &attr) < 0) {
perror("KVM_XEN_VCPU_SET_ATTR");
// This might fail if CONFIG_KVM_XEN is not enabled, but that's not the target bug
return 1;
}
// 6. Wait for the hrtimer to expire.
// This timer is armed in HRTIMER_MODE_ABS_HARD, meaning it will fire
// in hardirq context. The kernel must be compiled with PREEMPT_RT=y
// for this to trigger the sleeping function call bug.
printf("Waiting for timer to expire...\n");
sleep(2); // Sleep for longer than the timer expiration
printf("Program finished. If PREEMPT_RT kernel is running, a kernel panic may have occurred.\n");
return 0;
}
```
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action |
If |
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Args:
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action |
merge-strategy |
0m
Results: map[CurrentReproStrategy:An analysis of the bug report reveals that this is a PREEMPT_RT specific issue in the KVM Xen emulation code.
### Bug Analysis
1. **Context**: The bug is a "sleeping function called from invalid context" which occurs in a kernel compiled with `CONFIG_PREEMPT_RT`.
2. **Trigger**: The stack trace shows that the high-resolution timer callback `xen_timer_callback()` executes in hardirq context (as it is armed with `HRTIMER_MODE_ABS_HARD`).
3. **Root Cause**: `xen_timer_callback()` calls `kvm_xen_set_evtchn_fast()`, which unconditionally attempts to acquire a read lock on `gpc->lock` (a `rwlock_t`) via `read_lock_irqsave()`. In PREEMPT_RT kernels, `rwlock_t` is mapped to a sleeping lock (`rt_read_lock`). Acquiring a sleeping lock in hardirq context is invalid and triggers the BUG.
4. **Path to Reproduce**: We can trigger this by simply creating a KVM VM and VCPU, and then using the `KVM_XEN_VCPU_SET_ATTR` ioctl to arm the Xen timer (`KVM_XEN_VCPU_ATTR_TYPE_TIMER`). If we set the timer expiration to a short time in the future, `kvm_xen_start_timer()` will arm the hrtimer asynchronously. When the timer expires, it fires in hardirq context and hits the invalid lock acquisition.
### Reproduction Strategy
We can reproduce this issue with a minimal C program that:
1. Opens `/dev/kvm` and creates a VM and a VCPU.
2. Calls the `KVM_XEN_VCPU_SET_ATTR` ioctl on the VCPU to set up a Xen timer.
3. Sets the timer's `expires_ns` to a value safely in the future (e.g., 1 second) to ensure the timer is armed asynchronously rather than firing synchronously during the ioctl.
4. Sleeps to allow the timer to expire and trigger the bug in the interrupt context.
### Minimal C Reproducer
```c
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
/* Define KVM Xen constants in case they are missing from older headers */
#ifndef KVM_XEN_VCPU_ATTR_TYPE_TIMER
#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
#endif
#ifndef KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL
#define KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL ((uint32_t)(-1))
#endif
/* Local definition of the attribute struct to ensure compilation */
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
#define MY_KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
int main(void)
{
int kvm_fd, vm_fd, vcpu_fd;
struct my_kvm_xen_vcpu_attr attr = {0};
kvm_fd = open("/dev/kvm", O_RDWR);
if (kvm_fd < 0) {
perror("open /dev/kvm");
return 1;
}
vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0);
if (vm_fd < 0) {
perror("KVM_CREATE_VM");
return 1;
}
vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);
if (vcpu_fd < 0) {
perror("KVM_CREATE_VCPU");
return 1;
}
/*
* Arm the Xen timer.
* The guest kvmclock starts at 0 when the VM is created.
* Setting expires_ns to 1 second ensures delta > 0, forcing
* the hrtimer to be armed asynchronously.
*/
attr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
attr.u.timer.port = 1;
attr.u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
attr.u.timer.expires_ns = 1000000000ULL; /* 1 second */
if (ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr) < 0) {
perror("KVM_XEN_VCPU_SET_ATTR");
return 1;
}
/* Wait for the hrtimer to fire in hardirq context */
sleep(2);
return 0;
}
```]
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agent |
repro-generator |
0m
Model:
Results: map[IsProbe:true RawCandidateReproC:#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
int main(void)
{
int fd = open("/dev/kvm", O_RDWR);
if (fd < 0) {
printf("[-] Failed to open /dev/kvm: %s\n", strerror(errno));
exit(1);
}
printf("[+] open /dev/kvm successful.\n");
close(fd);
return 0;
}
]
Instruction: You are a security researcher with deep Linux kernel background.
Your goal is to generate a minimal, standalone C program for the strictly defensive
purpose of verifying a bugfix in an isolated environment.
To ensure that we can diagnose why a program might fail to run on the test environment,
you MUST include detailed logging and error checking in the generated C program:
1. Use 'printf(...)' for all progress messages and error logs.
2. Every system call (e.g., socket, bind, listen, connect, ioctl, send) must check for a failure return value.
3. If a call fails, it must print a specific error message including the function name
and the error string (use strerror(errno)), and then exit with a non-zero status.
4. The program must print a message after every successful major step.
5. Generate code that follows this pattern for all operations:
int res = do_something();
if (res < 0) {
printf("[-] Failed to do_something: %s\n", strerror(errno));
exit(1);
}
printf("[+] do_something successful.\n");
6. The compilation and development environment (including compilers, build
systems, makefiles, and kernel build/header directories) is NOT available
on the target test VM guest. Do NOT check for, build, or reference any
compilation tools, build files, or kernel development directories.
7. Do NOT execute shell commands or run external binaries (e.g. by using
functions like 'system()', 'popen()', or the 'exec' family such as
'execve()'). All environment checks, capability probings, and reproduction
steps must be performed directly using standard Linux system calls (such
as 'open', 'socket', 'ioctl', 'stat', etc.).
8. When reproducing asynchronous kernel timeouts or warnings, always
include a sufficient delay (using sleep or similar) after deleting
or unregistering the device to allow the kernel's asynchronous
timeout to trigger before program exit.
=== PHASE 1: CAPABILITY PROBING (GENERATION) ===
You MUST start by generating a simple 'probe' program first. This is a strict, non-negotiable requirement
to verify that the test environment has the necessary kernel capabilities and privileges.
This program's sole purpose is to verify subsystem availability and privileges by probing specific
device files, subsystems, or syscalls (for example: opening /dev/vhci to check if the virtual
Bluetooth controller is accessible, loading a minimal dummy BPF program, or making a specific
socket/ioctl call).
Print clear messages indicating success or failure of these probes, and exit with 0 only if
all checks pass.
Do NOT attempt complex logic, and do NOT try to trigger the actual bug/crash in this first version,
regardless of how simple the reproducer seems. You must wait until a successful probe run has been
confirmed in the environment (i.e., when CapabilitiesVerified becomes true).
Prefer calling several tools at the same time to save round-trips.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt: Bug Description: BUG: sleeping function called from invalid context in kvm_xen_set_evtchn_fast
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:248
in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 5622, name: syz-executor363
preempt_count: 10000, expected: 0
RCU nest depth: 1, expected: 1
locks held by syz-executor363/5622: 4, last CPU#0:
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: __simple_recursive_removal+0x19a/0x520 fs/libfs.c:619
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
#2: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rtlock_slowlock_locked+0x2ab/0x3c20 kernel/locking/rtmutex.c:1874
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1be/0x990 arch/x86/kvm/xen.c:1827
irq event stamp: 13272
hardirqs last enabled at (13271): [<ffffffff8b53b4b3>] __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:187 [inline]
hardirqs last enabled at (13271): [<ffffffff8b53b4b3>] _raw_spin_unlock_irq+0x23/0x50 kernel/locking/spinlock.c:206
hardirqs last disabled at (13272): [<ffffffff8b501aee>] sysvec_apic_timer_interrupt+0xe/0xc0 arch/x86/kernel/apic/apic.c:1062
softirqs last enabled at (6940): [<ffffffff81882fe0>] __local_bh_enable_ip+0x1a0/0x2b0 kernel/softirq.c:305
softirqs last disabled at (6932): [<ffffffff891cda09>] local_bh_disable include/linux/bottom_half.h:20 [inline]
softirqs last disabled at (6932): [<ffffffff891cda09>] __alloc_skb+0x189/0x7a0 net/core/skbuff.c:697
Preemption disabled at:
[<ffffffff81883b8e>] irq_enter_rcu+0x1e/0x1f0 kernel/softirq.c:668
CPU: 0 UID: 0 PID: 5622 Comm: syz-executor363 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
__might_resched+0x329/0x480 kernel/sched/core.c:9194
rt_read_lock+0xa9/0x4b0 kernel/locking/spinlock_rt.c:248
kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x3a0/0xaf0 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x44a/0x900 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:rt_mutex_owner include/linux/rtmutex.h:52 [inline]
RIP: 0010:rtmutex_spin_on_owner kernel/locking/rtmutex.c:1504 [inline]
RIP: 0010:rtlock_slowlock_locked+0x34e5/0x3c20 kernel/locking/rtmutex.c:1893
Code: 80 3c 01 00 4c 8b b4 24 80 00 00 00 4c 8b 2c 24 74 08 4c 89 ef e8 db 0e df f6 48 8d 84 24 60 01 00 00 49 39 45 00 75 6c f3 90 <48> b8 00 00 00 00 00 fc ff df 48 8b 8c 24 a8 00 00 00 80 3c 01 00
RSP: 0018:ffffc90004e6f7a0 EFLAGS: 00000246
RAX: ffffc90004e6f900 RBX: 1ffff11006ff9bbe RCX: 1ffffffff1ca7871
RDX: 00000000e6b90d15 RSI: ffffffff8bcbd060 RDI: 0000000000000001
RBP: ffffc90004e6f9f0 R08: 1d00000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8e3c3880 R12: ffff888037fcddc0
R13: ffffffff8e53c388 R14: ffffffff8e53c390 R15: 1ffff11006ff9bba
rtlock_slowlock kernel/locking/rtmutex.c:1922 [inline]
rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
__rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
rt_spin_lock+0x165/0x400 kernel/locking/spinlock_rt.c:57
spin_lock include/linux/spinlock_rt.h:45 [inline]
simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
__simple_recursive_removal+0x215/0x520 fs/libfs.c:623
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:781
kvm_destroy_vm_debugfs virt/kvm/kvm_main.c:988 [inline]
kvm_destroy_vm virt/kvm/kvm_main.c:1261 [inline]
kvm_put_kvm+0x147/0xae0 virt/kvm/kvm_main.c:1331
kvm_vm_release+0x46/0x50 virt/kvm/kvm_main.c:1354
__fput+0x42a/0xa80 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x73a/0x2360 kernel/exit.c:1009
do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
__do_sys_exit_group kernel/exit.c:1163 [inline]
__se_sys_exit_group kernel/exit.c:1161 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1161
x64_sys_call+0x18bf/0x18c0 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f132ec60d05
Code: Unable to access opcode bytes at 0x7f132ec60cdb.
RSP: 002b:00007ffe413e3968 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f132ec60d05
RDX: 00000000000000e7 RSI: ffffffffffffffd8 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000009 R11: 0000000000000202 R12: 0000000000000000
R13: 00007f132ecfa118 R14: 00007f132ecfc3c8 R15: 00007f132ecfc3e0
</TASK>
=============================
[ BUG: Invalid wait context ]
syzkaller #0 Tainted: G W
-----------------------------
syz-executor363/5622 is trying to lock:
ffff888038241530 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
other info that might help us debug this:
context-{2:2}
locks held by syz-executor363/5622: 4, last CPU#0:
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: __simple_recursive_removal+0x19a/0x520 fs/libfs.c:619
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
#2: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rtlock_slowlock_locked+0x2ab/0x3c20 kernel/locking/rtmutex.c:1874
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1be/0x990 arch/x86/kvm/xen.c:1827
stack backtrace:
CPU: 0 UID: 0 PID: 5622 Comm: syz-executor363 Tainted: G W syzkaller #0 PREEMPT_{RT,(full)}
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_lock_invalid_wait_context kernel/locking/lockdep.c:4846 [inline]
check_wait_context kernel/locking/lockdep.c:4918 [inline]
__lock_acquire+0xef0/0x2e40 kernel/locking/lockdep.c:5204
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5906
rt_read_lock+0xcc/0x4b0 kernel/locking/spinlock_rt.c:249
kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x3a0/0xaf0 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x44a/0x900 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:rt_mutex_owner include/linux/rtmutex.h:52 [inline]
RIP: 0010:rtmutex_spin_on_owner kernel/locking/rtmutex.c:1504 [inline]
RIP: 0010:rtlock_slowlock_locked+0x34e5/0x3c20 kernel/locking/rtmutex.c:1893
Code: 80 3c 01 00 4c 8b b4 24 80 00 00 00 4c 8b 2c 24 74 08 4c 89 ef e8 db 0e df f6 48 8d 84 24 60 01 00 00 49 39 45 00 75 6c f3 90 <48> b8 00 00 00 00 00 fc ff df 48 8b 8c 24 a8 00 00 00 80 3c 01 00
RSP: 0018:ffffc90004e6f7a0 EFLAGS: 00000246
RAX: ffffc90004e6f900 RBX: 1ffff11006ff9bbe RCX: 1ffffffff1ca7871
RDX: 00000000e6b90d15 RSI: ffffffff8bcbd060 RDI: 0000000000000001
RBP: ffffc90004e6f9f0 R08: 1d00000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8e3c3880 R12: ffff888037fcddc0
R13: ffffffff8e53c388 R14: ffffffff8e53c390 R15: 1ffff11006ff9bba
rtlock_slowlock kernel/locking/rtmutex.c:1922 [inline]
rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
__rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
rt_spin_lock+0x165/0x400 kernel/locking/spinlock_rt.c:57
spin_lock include/linux/spinlock_rt.h:45 [inline]
simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
__simple_recursive_removal+0x215/0x520 fs/libfs.c:623
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:781
kvm_destroy_vm_debugfs virt/kvm/kvm_main.c:988 [inline]
kvm_destroy_vm virt/kvm/kvm_main.c:1261 [inline]
kvm_put_kvm+0x147/0xae0 virt/kvm/kvm_main.c:1331
kvm_vm_release+0x46/0x50 virt/kvm/kvm_main.c:1354
__fput+0x42a/0xa80 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x73a/0x2360 kernel/exit.c:1009
do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
__do_sys_exit_group kernel/exit.c:1163 [inline]
__se_sys_exit_group kernel/exit.c:1161 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1161
x64_sys_call+0x18bf/0x18c0 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f132ec60d05
Code: Unable to access opcode bytes at 0x7f132ec60cdb.
RSP: 002b:00007ffe413e3968 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f132ec60d05
RDX: 00000000000000e7 RSI: ffffffffffffffd8 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000009 R11: 0000000000000202 R12: 0000000000000000
R13: 00007f132ecfa118 R14: 00007f132ecfc3c8 R15: 00007f132ecfc3e0
</TASK>
----------------
Code disassembly (best guess):
0: 80 3c 01 00 cmpb $0x0,(%rcx,%rax,1)
4: 4c 8b b4 24 80 00 00 mov 0x80(%rsp),%r14
b: 00
c: 4c 8b 2c 24 mov (%rsp),%r13
10: 74 08 je 0x1a
12: 4c 89 ef mov %r13,%rdi
15: e8 db 0e df f6 call 0xf6df0ef5
1a: 48 8d 84 24 60 01 00 lea 0x160(%rsp),%rax
21: 00
22: 49 39 45 00 cmp %rax,0x0(%r13)
26: 75 6c jne 0x94
28: f3 90 pause
* 2a: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax <-- trapping instruction
31: fc ff df
34: 48 8b 8c 24 a8 00 00 mov 0xa8(%rsp),%rcx
3b: 00
3c: 80 3c 01 00 cmpb $0x0,(%rcx,%rax,1)
Strategy: An analysis of the bug report reveals that this is a PREEMPT_RT specific issue in the KVM Xen emulation code.
### Bug Analysis
1. **Context**: The bug is a "sleeping function called from invalid context" which occurs in a kernel compiled with `CONFIG_PREEMPT_RT`.
2. **Trigger**: The stack trace shows that the high-resolution timer callback `xen_timer_callback()` executes in hardirq context (as it is armed with `HRTIMER_MODE_ABS_HARD`).
3. **Root Cause**: `xen_timer_callback()` calls `kvm_xen_set_evtchn_fast()`, which unconditionally attempts to acquire a read lock on `gpc->lock` (a `rwlock_t`) via `read_lock_irqsave()`. In PREEMPT_RT kernels, `rwlock_t` is mapped to a sleeping lock (`rt_read_lock`). Acquiring a sleeping lock in hardirq context is invalid and triggers the BUG.
4. **Path to Reproduce**: We can trigger this by simply creating a KVM VM and VCPU, and then using the `KVM_XEN_VCPU_SET_ATTR` ioctl to arm the Xen timer (`KVM_XEN_VCPU_ATTR_TYPE_TIMER`). If we set the timer expiration to a short time in the future, `kvm_xen_start_timer()` will arm the hrtimer asynchronously. When the timer expires, it fires in hardirq context and hits the invalid lock acquisition.
### Reproduction Strategy
We can reproduce this issue with a minimal C program that:
1. Opens `/dev/kvm` and creates a VM and a VCPU.
2. Calls the `KVM_XEN_VCPU_SET_ATTR` ioctl on the VCPU to set up a Xen timer.
3. Sets the timer's `expires_ns` to a value safely in the future (e.g., 1 second) to ensure the timer is armed asynchronously rather than firing synchronously during the ioctl.
4. Sleeps to allow the timer to expire and trigger the bug in the interrupt context.
### Minimal C Reproducer
```c
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
/* Define KVM Xen constants in case they are missing from older headers */
#ifndef KVM_XEN_VCPU_ATTR_TYPE_TIMER
#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
#endif
#ifndef KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL
#define KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL ((uint32_t)(-1))
#endif
/* Local definition of the attribute struct to ensure compilation */
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
#define MY_KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
int main(void)
{
int kvm_fd, vm_fd, vcpu_fd;
struct my_kvm_xen_vcpu_attr attr = {0};
kvm_fd = open("/dev/kvm", O_RDWR);
if (kvm_fd < 0) {
perror("open /dev/kvm");
return 1;
}
vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0);
if (vm_fd < 0) {
perror("KVM_CREATE_VM");
return 1;
}
vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);
if (vcpu_fd < 0) {
perror("KVM_CREATE_VCPU");
return 1;
}
/*
* Arm the Xen timer.
* The guest kvmclock starts at 0 when the VM is created.
* Setting expires_ns to 1 second ensures delta > 0, forcing
* the hrtimer to be armed asynchronously.
*/
attr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
attr.u.timer.port = 1;
attr.u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
attr.u.timer.expires_ns = 1000000000ULL; /* 1 second */
if (ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr) < 0) {
perror("KVM_XEN_VCPU_SET_ATTR");
return 1;
}
/* Wait for the hrtimer to fire in hardirq context */
sleep(2);
return 0;
}
```
|
| 65/4 |
2026/08/12 13:19 |
llm |
repro-generator |
0m
Model:
Tokens:
input: 10747
output: 168
thoughts: 541
Thoughts: **My Thought Process for Generating the KVM Xen Bugfix Verification Probe**
My primary objective here is to create a minimal, standalone C program. The ultimate goal of this program is to verify a bugfix, specifically one identified as "BUG: sleeping function called from invalid context in kvm_xen_set_evtchn_fast." This particular bug is a PREEMPT_RT specific issue within the KVM Xen emulation.
I've been presented with a strategy and even a minimal C reproducer for the bug itself. However, the instructions are very clear and non-negotiable: I **MUST** start by generating a simple 'probe' program. The purpose of this probe is critical: it's to confirm that the test environment possesses the necessary kernel capabilities and privileges for the actual bug reproducer to function correctly.
To achieve this, the probe program needs to investigate the availability of specific subsystems and verify the user's privileges. The provided reproducer, in its current form, relies on accessing the `/dev/kvm` device file. Therefore, my probe program's core functionality should be to attempt to open `/dev/kvm`. I need to check if this operation succeeds. If it does, the program should exit cleanly with a status code of 0. Crucially, it must also provide clear, informative messages to the user about its progress and any outcomes.
With these requirements in mind, I've drafted the probe program:
```c
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
int main(void)
{
int fd = open("/dev/kvm", O_RDWR);
if (fd < 0) {
printf("[-] Failed to open /dev/kvm: %s\n", strerror(errno));
exit(1);
}
printf("[+] open /dev/kvm successful.\n");
close(fd);
return 0;
}
```
Now, I'm performing a rigorous check against all the specified requirements to ensure this probe program is compliant:
1. **'printf(...)' for all messages:** I've used `printf` for both informational messages and error logging. This is adhered to.
2. **Check for failure return values:** Every system call I've made, specifically `open`, is checked for a failure return value (`fd < 0`). This is satisfied.
3. **Specific error messages and exit codes:** If a call fails, I'm printing a clear message that includes the operation (`open /dev/kvm`) and the specific error using `strerror(errno)`. The program then exits with a non-zero status code (1). This is covered.
4. **Success messages:** After a successful major step (in this case, opening `/dev/kvm`), I print a success message. This is done.
5. **Following the pattern:** The code strictly follows the `res = do_something(); if (res < 0) {...} else {...}` pattern, which is perfect for robustness.
6. **No compilation/build checks:** The output is solely the C code; no compilation commands are included. This requirement is met.
7. **No shell commands:** No external shell commands are being invoked. This is also satisfied.
8. **Wait for async timeouts:** This is not applicable to a simple probe program like this, so it's not a concern.
Based on this detailed review, the probe program appears to be perfectly aligned with all the stipulated requirements. My next step will be to use the `set-results` tool to formally present these findings.
|
| 66/4 |
2026/08/12 13:19 |
tool |
set-results |
0m
Args: map[IsProbe:true RawCandidateReproC:#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
int main(void)
{
int fd = open("/dev/kvm", O_RDWR);
if (fd < 0) {
printf("[-] Failed to open /dev/kvm: %s\n", strerror(errno));
exit(1);
}
printf("[+] open /dev/kvm successful.\n");
close(fd);
return 0;
}
]
Results: map[IsProbe:true RawCandidateReproC:#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
int main(void)
{
int fd = open("/dev/kvm", O_RDWR);
if (fd < 0) {
printf("[-] Failed to open /dev/kvm: %s\n", strerror(errno));
exit(1);
}
printf("[+] open /dev/kvm successful.\n");
close(fd);
return 0;
}
]
|
| 67/3 |
2026/08/12 13:19 |
loop |
|
0m
|
| 68/4 |
2026/08/12 13:19 |
iteration |
0 |
0m
|
| 69/5 |
2026/08/12 13:19 |
action |
merge-repro-c |
0m
Results: map[CurrentCandidateReproC:#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
int main(void)
{
int fd = open("/dev/kvm", O_RDWR);
if (fd < 0) {
printf("[-] Failed to open /dev/kvm: %s\n", strerror(errno));
exit(1);
}
printf("[+] open /dev/kvm successful.\n");
close(fd);
return 0;
}
]
|
| 70/5 |
2026/08/12 13:19 |
action |
compile-c-prog |
0m
Results: map[CompilerError: FormattedReproC:#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
int main(void)
{
int fd = open("/dev/kvm", O_RDWR);
if (fd < 0) {
printf("[-] Failed to open /dev/kvm: %s\n", strerror(errno));
exit(1);
}
printf("[+] open /dev/kvm successful.\n");
close(fd);
return 0;
}
]
|
| 71/5 |
2026/08/12 13:19 |
action |
If |
0m
Args:
|
| 72/3 |
2026/08/12 13:19 |
action |
run-c-repro |
4m
Results: map[CandidateBugTitle: CandidateCrashReport: CandidateReproduced:false ConsoleOutput:[ 109.289144][ T33] kauditd_printk_skb: 10 callbacks suppressed
[ 109.289162][ T33] audit: type=1400 audit(1786540887.283:201): avc: denied { transition } for pid=5827 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 109.307328][ T33] audit: type=1400 audit(1786540887.283:202): avc: denied { noatsecure } for pid=5827 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 109.326071][ T33] audit: type=1400 audit(1786540887.283:203): avc: denied { rlimitinh } for pid=5827 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 109.336022][ T33] audit: type=1400 audit(1786540887.283:204): avc: denied { siginh } for pid=5827 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 113.204701][ T33] audit: type=1400 audit(1786540891.193:205): avc: denied { write } for pid=5832 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 113.328998][ T33] audit: type=1400 audit(1786540891.323:206): avc: denied { write } for pid=5836 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 113.590554][ T33] audit: type=1400 audit(1786540891.583:207): avc: denied { write } for pid=5839 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 113.678023][ T33] audit: type=1400 audit(1786540891.673:208): avc: denied { write } for pid=5842 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.263311][ T33] audit: type=1400 audit(1786540892.263:209): avc: denied { write } for pid=5845 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.432685][ T33] audit: type=1400 audit(1786540892.433:210): avc: denied { write } for pid=5848 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.614255][ T33] audit: type=1400 audit(1786540892.613:211): avc: denied { write } for pid=5851 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.745954][ T33] audit: type=1400 audit(1786540892.743:212): avc: denied { write } for pid=5854 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.942742][ T33] audit: type=1400 audit(1786540892.933:213): avc: denied { write } for pid=5857 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.067169][ T33] audit: type=1400 audit(1786540893.063:214): avc: denied { write } for pid=5861 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.222089][ T33] audit: type=1400 audit(1786540893.213:215): avc: denied { write } for pid=5865 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.447584][ T33] audit: type=1400 audit(1786540893.443:216): avc: denied { write } for pid=5870 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.634398][ T33] audit: type=1400 audit(1786540893.633:217): avc: denied { write } for pid=5873 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.722229][ T33] audit: type=1400 audit(1786540893.713:218): avc: denied { write } for pid=5876 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.869451][ T33] audit: type=1400 audit(1786540893.863:219): avc: denied { write } for pid=5879 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:56509' (ED25519) to the list of known hosts.
[+] open /dev/kvm successful.
OtherCrashReports:<nil> StraceOutput:/strace -e \!wait4,clock_nanosleep,nanosleep -s 100 -x -f /syz-executor519858962
<...>
[ 116.266896][ T33] kauditd_printk_skb: 10 callbacks suppressed
[ 116.266911][ T33] audit: type=1400 audit(1786541031.945:201): avc: denied { transition } for pid=5834 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 116.280441][ T33] audit: type=1400 audit(1786541031.945:202): avc: denied { noatsecure } for pid=5834 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 116.288398][ T33] audit: type=1400 audit(1786541031.945:203): avc: denied { rlimitinh } for pid=5834 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 116.298705][ T33] audit: type=1400 audit(1786541031.945:204): avc: denied { siginh } for pid=5834 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 120.332930][ T33] audit: type=1400 audit(1786541036.015:205): avc: denied { write } for pid=5840 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.427959][ T33] audit: type=1400 audit(1786541036.105:206): avc: denied { write } for pid=5843 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.574091][ T33] audit: type=1400 audit(1786541036.245:207): avc: denied { write } for pid=5846 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.666332][ T33] audit: type=1400 audit(1786541036.345:208): avc: denied { write } for pid=5849 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.818953][ T33] audit: type=1400 audit(1786541036.495:209): avc: denied { write } for pid=5852 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.911900][ T33] audit: type=1400 audit(1786541036.595:210): avc: denied { write } for pid=5855 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.309812][ T33] kauditd_printk_skb: 2 callbacks suppressed
[ 121.309828][ T33] audit: type=1400 audit(1786541036.985:213): avc: denied { write } for pid=5864 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.405176][ T33] audit: type=1400 audit(1786541037.085:214): avc: denied { write } for pid=5867 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.710149][ T33] audit: type=1400 audit(1786541037.385:215): avc: denied { write } for pid=5870 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.811771][ T33] audit: type=1400 audit(1786541037.495:216): avc: denied { write } for pid=5873 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.576398][ T33] audit: type=1400 audit(1786541038.255:217): avc: denied { write } for pid=5881 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.719657][ T33] audit: type=1400 audit(1786541038.395:218): avc: denied { write } for pid=5884 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.967984][ T33] audit: type=1400 audit(1786541038.645:219): avc: denied { write } for pid=5888 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 123.079453][ T33] audit: type=1400 audit(1786541038.755:220): avc: denied { write } for pid=5893 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:48211' (ED25519) to the list of known hosts.
execve("/syz-executor519858962", ["/syz-executor519858962"], 0x7ffede00a5f0 /* 11 vars */) = 0
brk(NULL) = 0x555583994000
brk(0x555583994d80) = 0x555583994d80
arch_prctl(ARCH_SET_FS, 0x555583994400) = 0
set_tid_address(0x5555839946d0) = 5910
set_robust_list(0x5555839946e0, 24) = 0
rseq({cpu_id_start=0, cpu_id=RSEQ_CPU_ID_UNINITIALIZED, rseq_cs=NULL, flags=0, node_id=0, mm_cid=0, slice_ctrl={request=0, granted=0, __reserved=0}, __reserved=0}, 33, 0, 0x53053053) = 0
prlimit64(0, RLIMIT_STACK, NULL, {rlim_cur=8192*1024, rlim_max=RLIM64_INFINITY}) = 0
readlinkat(AT_FDCWD, "/proc/self/exe", "/syz-executor519858962", 4096) = 22
getrandom("\x3d\x2d\x47\x7e\x7a\xd7\x3d\xf3", 8, GRND_NONBLOCK) = 8
brk(NULL) = 0x555583994d80
brk(0x5555839b5d80) = 0x5555839b5d80
brk(0x5555839b6000) = 0x5555839b6000
mprotect(0x7f78e0a9b000, 20480, PROT_READ) = 0
[ 125.608544][ T33] audit: type=1400 audit(1786541041.285:221): avc: denied { read write } for pid=5910 comm="syz-executor519" name="kvm" dev="devtmpfs" ino=84 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:kvm_device_t tclass=chr_file permissive=1
openat(AT_FDCWD, "/dev/kvm", O_RDWR) = 3
[ 125.623663][ T33] audit: type=1400 audit(1786541041.295:222): avc: denied { open } for pid=5910 comm="syz-executor519" path="/dev/kvm" dev="devtmpfs" ino=84 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:kvm_device_t tclass=chr_file permissive=1
fstat(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
close(3) = 0
[+] open /dev/kvm successful.
write(1, "[+] open /dev/kvm successful.\n", 30) = 30
exit_group(0) = ?
+++ exited with 0 +++
[ 134.874303][ T1377] ieee802154 phy0 wpan0: encryption failed: -22
[ 134.881697][ T1377] ieee802154 phy1 wpan1: encryption failed: -22
TestError:]
|
| 73/3 |
2026/08/12 13:24 |
action |
truncate-log |
0m
Results: map[TruncatedConsoleOutput:[ 109.289144][ T33] kauditd_printk_skb: 10 callbacks suppressed
[ 109.289162][ T33] audit: type=1400 audit(1786540887.283:201): avc: denied { transition } for pid=5827 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 109.307328][ T33] audit: type=1400 audit(1786540887.283:202): avc: denied { noatsecure } for pid=5827 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 109.326071][ T33] audit: type=1400 audit(1786540887.283:203): avc: denied { rlimitinh } for pid=5827 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 109.336022][ T33] audit: type=1400 audit(1786540887.283:204): avc: denied { siginh } for pid=5827 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 113.204701][ T33] audit: type=1400 audit(1786540891.193:205): avc: denied { write } for pid=5832 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 113.328998][ T33] audit: type=1400 audit(1786540891.323:206): avc: denied { write } for pid=5836 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 113.590554][ T33] audit: type=1400 audit(1786540891.583:207): avc: denied { write } for pid=5839 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 113.678023][ T33] audit: type=1400 audit(1786540891.673:208): avc: denied { write } for pid=5842 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.263311][ T33] audit: type=1400 audit(1786540892.263:209): avc: denied { write } for pid=5845 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.432685][ T33] audit: type=1400 audit(1786540892.433:210): avc: denied { write } for pid=5848 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.614255][ T33] audit: type=1400 audit(1786540892.613:211): avc: denied { write } for pid=5851 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.745954][ T33] audit: type=1400 audit(1786540892.743:212): avc: denied { write } for pid=5854 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.942742][ T33] audit: type=1400 audit(1786540892.933:213): avc: denied { write } for pid=5857 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.067169][ T33] audit: type=1400 audit(1786540893.063:214): avc: denied { write } for pid=5861 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.222089][ T33] audit: type=1400 audit(1786540893.213:215): avc: denied { write } for pid=5865 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.447584][ T33] audit: type=1400 audit(1786540893.443:216): avc: denied { write } for pid=5870 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.634398][ T33] audit: type=1400 audit(1786540893.633:217): avc: denied { write } for pid=5873 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.722229][ T33] audit: type=1400 audit(1786540893.713:218): avc: denied { write } for pid=5876 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.869451][ T33] audit: type=1400 audit(1786540893.863:219): avc: denied { write } for pid=5879 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:56509' (ED25519) to the list of known hosts.
[+] open /dev/kvm successful.
TruncatedCrashReport: TruncatedStraceOutput:/strace -e \!wait4,clock_nanosleep,nanosleep -s 100 -x -f /syz-executor519858962
<...>
[ 116.266896][ T33] kauditd_printk_skb: 10 callbacks suppressed
[ 116.266911][ T33] audit: type=1400 audit(1786541031.945:201): avc: denied { transition } for pid=5834 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 116.280441][ T33] audit: type=1400 audit(1786541031.945:202): avc: denied { noatsecure } for pid=5834 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 116.288398][ T33] audit: type=1400 audit(1786541031.945:203): avc: denied { rlimitinh } for pid=5834 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 116.298705][ T33] audit: type=1400 audit(1786541031.945:204): avc: denied { siginh } for pid=5834 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 120.332930][ T33] audit: type=1400 audit(1786541036.015:205): avc: denied { write } for pid=5840 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.427959][ T33] audit: type=1400 audit(1786541036.105:206): avc: denied { write } for pid=5843 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.574091][ T33] audit: type=1400 audit(1786541036.245:207): avc: denied { write } for pid=5846 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.666332][ T33] audit: type=1400 audit(1786541036.345:208): avc: denied { write } for pid=5849 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.818953][ T33] audit: type=1400 audit(1786541036.495:209): avc: denied { write } for pid=5852 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.911900][ T33] audit: type=1400 audit(1786541036.595:210): avc: denied { write } for pid=5855 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.309812][ T33] kauditd_printk_skb: 2 callbacks suppressed
[ 121.309828][ T33] audit: type=1400 audit(1786541036.985:213): avc: denied { write } for pid=5864 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.405176][ T33] audit: type=1400 audit(1786541037.085:214): avc: denied { write } for pid=5867 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.710149][ T33] audit: type=1400 audit(1786541037.385:215): avc: denied { write } for pid=5870 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.811771][ T33] audit: type=1400 audit(1786541037.495:216): avc: denied { write } for pid=5873 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.576398][ T33] audit: type=1400 audit(1786541038.255:217): avc: denied { write } for pid=5881 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.719657][ T33] audit: type=1400 audit(1786541038.395:218): avc: denied { write } for pid=5884 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.967984][ T33] audit: type=1400 audit(1786541038.645:219): avc: denied { write } for pid=5888 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 123.079453][ T33] audit: type=1400 audit(1786541038.755:220): avc: denied { write } for pid=5893 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:48211' (ED25519) to the list of known hosts.
execve("/syz-executor519858962", ["/syz-executor519858962"], 0x7ffede00a5f0 /* 11 vars */) = 0
brk(NULL) = 0x555583994000
brk(0x555583994d80) = 0x555583994d80
arch_prctl(ARCH_SET_FS, 0x555583994400) = 0
set_tid_address(0x5555839946d0) = 5910
set_robust_list(0x5555839946e0, 24) = 0
rseq({cpu_id_start=0, cpu_id=RSEQ_CPU_ID_UNINITIALIZED, rseq_cs=NULL, flags=0, node_id=0, mm_cid=0, slice_ctrl={request=0, granted=0, __reserved=0}, __reserved=0}, 33, 0, 0x53053053) = 0
prlimit64(0, RLIMIT_STACK, NULL, {rlim_cur=8192*1024, rlim_max=RLIM64_INFINITY}) = 0
readlinkat(AT_FDCWD, "/proc/self/exe", "/syz-executor519858962", 4096) = 22
getrandom("\x3d\x2d\x47\x7e\x7a\xd7\x3d\xf3", 8, GRND_NONBLOCK) = 8
brk(NULL) = 0x555583994d80
brk(0x5555839b5d80) = 0x5555839b5d80
brk(0x5555839b6000) = 0x5555839b6000
mprotect(0x7f78e0a9b000, 20480, PROT_READ) = 0
[ 125.608544][ T33] audit: type=1400 audit(1786541041.285:221): avc: denied { read write } for pid=5910 comm="syz-executor519" name="kvm" dev="devtmpfs" ino=84 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:kvm_device_t tclass=chr_file permissive=1
openat(AT_FDCWD, "/dev/kvm", O_RDWR) = 3
[ 125.623663][ T33] audit: type=1400 audit(1786541041.295:222): avc: denied { open } for pid=5910 comm="syz-executor519" path="/dev/kvm" dev="devtmpfs" ino=84 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:kvm_device_t tclass=chr_file permissive=1
fstat(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
close(3) = 0
[+] open /dev/kvm successful.
write(1, "[+] open /dev/kvm successful.\n", 30) = 30
exit_group(0) = ?
+++ exited with 0 +++
[ 134.874303][ T1377] ieee802154 phy0 wpan0: encryption failed: -22
[ 134.881697][ T1377] ieee802154 phy1 wpan1: encryption failed: -22
]
|
| 74/3 |
2026/08/12 13:24 |
agent |
repro-oracle |
0m
Model:
Results: map[Feedback:The environment probe was successful. `/dev/kvm` is accessible. Please proceed to generate the full reproducer in the next iteration. ProbePassed:true TerminalError: TitleMatches:false]
Instruction: You are a security researcher with deep Linux kernel background.
Analyze the results of running the generated program.
=== CRITICAL ENVIRONMENT & TARGET CLASSIFICATION ===
Set 'TerminalError' to a descriptive error message ONLY if:
1. The execution failed due to missing hardware device nodes, subsystems, kernel modules, or privilege limits
that cannot be loaded, created, or bypassed by user-space C code edits in the VM guest.
2. The target source files or functions described in the bug description do not exist in the checked-out codebase,
meaning the codebase version is mismatched and the target code is absent.
=== CRITICAL PROHIBITIONS ===
- Do NOT classify a run as a terminal failure or assume a bug is fixed based on git log entries, commit titles,
or commit messages. Reproducibility can ONLY be determined by executing reproducer candidates in the VM.
- Do NOT suggest C code strategies, repairs, or namespace bypasses when setting 'TerminalError'.
=== PHASE 1: CAPABILITY PROBING (EVALUATION) ===
The executed program was a simple environment probe.
Use this to guide your classification and feedback:
1. If the execution was successful (all environment/subsystem probes passed and program exited with 0),
set the field 'ProbePassed' to true and provide feedback explicitly indicating that the environment
is ready and the agent should now proceed to generate the full reproducer in the next iteration.
2. If the probe failed (e.g., missing permissions, missing devices, or sandbox restrictions),
set the field 'ProbePassed' to false, and explain what failed in the 'Feedback'
field so the generator can adjust its setups.
Prefer calling several tools at the same time to save round-trips.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt: Bug Description: BUG: sleeping function called from invalid context in kvm_xen_set_evtchn_fast
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:248
in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 5622, name: syz-executor363
preempt_count: 10000, expected: 0
RCU nest depth: 1, expected: 1
locks held by syz-executor363/5622: 4, last CPU#0:
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: __simple_recursive_removal+0x19a/0x520 fs/libfs.c:619
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
#2: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rtlock_slowlock_locked+0x2ab/0x3c20 kernel/locking/rtmutex.c:1874
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1be/0x990 arch/x86/kvm/xen.c:1827
irq event stamp: 13272
hardirqs last enabled at (13271): [<ffffffff8b53b4b3>] __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:187 [inline]
hardirqs last enabled at (13271): [<ffffffff8b53b4b3>] _raw_spin_unlock_irq+0x23/0x50 kernel/locking/spinlock.c:206
hardirqs last disabled at (13272): [<ffffffff8b501aee>] sysvec_apic_timer_interrupt+0xe/0xc0 arch/x86/kernel/apic/apic.c:1062
softirqs last enabled at (6940): [<ffffffff81882fe0>] __local_bh_enable_ip+0x1a0/0x2b0 kernel/softirq.c:305
softirqs last disabled at (6932): [<ffffffff891cda09>] local_bh_disable include/linux/bottom_half.h:20 [inline]
softirqs last disabled at (6932): [<ffffffff891cda09>] __alloc_skb+0x189/0x7a0 net/core/skbuff.c:697
Preemption disabled at:
[<ffffffff81883b8e>] irq_enter_rcu+0x1e/0x1f0 kernel/softirq.c:668
CPU: 0 UID: 0 PID: 5622 Comm: syz-executor363 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
__might_resched+0x329/0x480 kernel/sched/core.c:9194
rt_read_lock+0xa9/0x4b0 kernel/locking/spinlock_rt.c:248
kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x3a0/0xaf0 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x44a/0x900 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:rt_mutex_owner include/linux/rtmutex.h:52 [inline]
RIP: 0010:rtmutex_spin_on_owner kernel/locking/rtmutex.c:1504 [inline]
RIP: 0010:rtlock_slowlock_locked+0x34e5/0x3c20 kernel/locking/rtmutex.c:1893
Code: 80 3c 01 00 4c 8b b4 24 80 00 00 00 4c 8b 2c 24 74 08 4c 89 ef e8 db 0e df f6 48 8d 84 24 60 01 00 00 49 39 45 00 75 6c f3 90 <48> b8 00 00 00 00 00 fc ff df 48 8b 8c 24 a8 00 00 00 80 3c 01 00
RSP: 0018:ffffc90004e6f7a0 EFLAGS: 00000246
RAX: ffffc90004e6f900 RBX: 1ffff11006ff9bbe RCX: 1ffffffff1ca7871
RDX: 00000000e6b90d15 RSI: ffffffff8bcbd060 RDI: 0000000000000001
RBP: ffffc90004e6f9f0 R08: 1d00000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8e3c3880 R12: ffff888037fcddc0
R13: ffffffff8e53c388 R14: ffffffff8e53c390 R15: 1ffff11006ff9bba
rtlock_slowlock kernel/locking/rtmutex.c:1922 [inline]
rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
__rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
rt_spin_lock+0x165/0x400 kernel/locking/spinlock_rt.c:57
spin_lock include/linux/spinlock_rt.h:45 [inline]
simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
__simple_recursive_removal+0x215/0x520 fs/libfs.c:623
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:781
kvm_destroy_vm_debugfs virt/kvm/kvm_main.c:988 [inline]
kvm_destroy_vm virt/kvm/kvm_main.c:1261 [inline]
kvm_put_kvm+0x147/0xae0 virt/kvm/kvm_main.c:1331
kvm_vm_release+0x46/0x50 virt/kvm/kvm_main.c:1354
__fput+0x42a/0xa80 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x73a/0x2360 kernel/exit.c:1009
do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
__do_sys_exit_group kernel/exit.c:1163 [inline]
__se_sys_exit_group kernel/exit.c:1161 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1161
x64_sys_call+0x18bf/0x18c0 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f132ec60d05
Code: Unable to access opcode bytes at 0x7f132ec60cdb.
RSP: 002b:00007ffe413e3968 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f132ec60d05
RDX: 00000000000000e7 RSI: ffffffffffffffd8 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000009 R11: 0000000000000202 R12: 0000000000000000
R13: 00007f132ecfa118 R14: 00007f132ecfc3c8 R15: 00007f132ecfc3e0
</TASK>
=============================
[ BUG: Invalid wait context ]
syzkaller #0 Tainted: G W
-----------------------------
syz-executor363/5622 is trying to lock:
ffff888038241530 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
other info that might help us debug this:
context-{2:2}
locks held by syz-executor363/5622: 4, last CPU#0:
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: __simple_recursive_removal+0x19a/0x520 fs/libfs.c:619
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
#2: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rtlock_slowlock_locked+0x2ab/0x3c20 kernel/locking/rtmutex.c:1874
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1be/0x990 arch/x86/kvm/xen.c:1827
stack backtrace:
CPU: 0 UID: 0 PID: 5622 Comm: syz-executor363 Tainted: G W syzkaller #0 PREEMPT_{RT,(full)}
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_lock_invalid_wait_context kernel/locking/lockdep.c:4846 [inline]
check_wait_context kernel/locking/lockdep.c:4918 [inline]
__lock_acquire+0xef0/0x2e40 kernel/locking/lockdep.c:5204
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5906
rt_read_lock+0xcc/0x4b0 kernel/locking/spinlock_rt.c:249
kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x3a0/0xaf0 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x44a/0x900 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:rt_mutex_owner include/linux/rtmutex.h:52 [inline]
RIP: 0010:rtmutex_spin_on_owner kernel/locking/rtmutex.c:1504 [inline]
RIP: 0010:rtlock_slowlock_locked+0x34e5/0x3c20 kernel/locking/rtmutex.c:1893
Code: 80 3c 01 00 4c 8b b4 24 80 00 00 00 4c 8b 2c 24 74 08 4c 89 ef e8 db 0e df f6 48 8d 84 24 60 01 00 00 49 39 45 00 75 6c f3 90 <48> b8 00 00 00 00 00 fc ff df 48 8b 8c 24 a8 00 00 00 80 3c 01 00
RSP: 0018:ffffc90004e6f7a0 EFLAGS: 00000246
RAX: ffffc90004e6f900 RBX: 1ffff11006ff9bbe RCX: 1ffffffff1ca7871
RDX: 00000000e6b90d15 RSI: ffffffff8bcbd060 RDI: 0000000000000001
RBP: ffffc90004e6f9f0 R08: 1d00000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8e3c3880 R12: ffff888037fcddc0
R13: ffffffff8e53c388 R14: ffffffff8e53c390 R15: 1ffff11006ff9bba
rtlock_slowlock kernel/locking/rtmutex.c:1922 [inline]
rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
__rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
rt_spin_lock+0x165/0x400 kernel/locking/spinlock_rt.c:57
spin_lock include/linux/spinlock_rt.h:45 [inline]
simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
__simple_recursive_removal+0x215/0x520 fs/libfs.c:623
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:781
kvm_destroy_vm_debugfs virt/kvm/kvm_main.c:988 [inline]
kvm_destroy_vm virt/kvm/kvm_main.c:1261 [inline]
kvm_put_kvm+0x147/0xae0 virt/kvm/kvm_main.c:1331
kvm_vm_release+0x46/0x50 virt/kvm/kvm_main.c:1354
__fput+0x42a/0xa80 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x73a/0x2360 kernel/exit.c:1009
do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
__do_sys_exit_group kernel/exit.c:1163 [inline]
__se_sys_exit_group kernel/exit.c:1161 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1161
x64_sys_call+0x18bf/0x18c0 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f132ec60d05
Code: Unable to access opcode bytes at 0x7f132ec60cdb.
RSP: 002b:00007ffe413e3968 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f132ec60d05
RDX: 00000000000000e7 RSI: ffffffffffffffd8 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000009 R11: 0000000000000202 R12: 0000000000000000
R13: 00007f132ecfa118 R14: 00007f132ecfc3c8 R15: 00007f132ecfc3e0
</TASK>
----------------
Code disassembly (best guess):
0: 80 3c 01 00 cmpb $0x0,(%rcx,%rax,1)
4: 4c 8b b4 24 80 00 00 mov 0x80(%rsp),%r14
b: 00
c: 4c 8b 2c 24 mov (%rsp),%r13
10: 74 08 je 0x1a
12: 4c 89 ef mov %r13,%rdi
15: e8 db 0e df f6 call 0xf6df0ef5
1a: 48 8d 84 24 60 01 00 lea 0x160(%rsp),%rax
21: 00
22: 49 39 45 00 cmp %rax,0x0(%r13)
26: 75 6c jne 0x94
28: f3 90 pause
* 2a: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax <-- trapping instruction
31: fc ff df
34: 48 8b 8c 24 a8 00 00 mov 0xa8(%rsp),%rcx
3b: 00
3c: 80 3c 01 00 cmpb $0x0,(%rcx,%rax,1)
IsProbe: true
Reproduced: false
Console Output: [ 109.289144][ T33] kauditd_printk_skb: 10 callbacks suppressed
[ 109.289162][ T33] audit: type=1400 audit(1786540887.283:201): avc: denied { transition } for pid=5827 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 109.307328][ T33] audit: type=1400 audit(1786540887.283:202): avc: denied { noatsecure } for pid=5827 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 109.326071][ T33] audit: type=1400 audit(1786540887.283:203): avc: denied { rlimitinh } for pid=5827 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 109.336022][ T33] audit: type=1400 audit(1786540887.283:204): avc: denied { siginh } for pid=5827 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 113.204701][ T33] audit: type=1400 audit(1786540891.193:205): avc: denied { write } for pid=5832 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 113.328998][ T33] audit: type=1400 audit(1786540891.323:206): avc: denied { write } for pid=5836 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 113.590554][ T33] audit: type=1400 audit(1786540891.583:207): avc: denied { write } for pid=5839 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 113.678023][ T33] audit: type=1400 audit(1786540891.673:208): avc: denied { write } for pid=5842 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.263311][ T33] audit: type=1400 audit(1786540892.263:209): avc: denied { write } for pid=5845 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.432685][ T33] audit: type=1400 audit(1786540892.433:210): avc: denied { write } for pid=5848 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.614255][ T33] audit: type=1400 audit(1786540892.613:211): avc: denied { write } for pid=5851 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.745954][ T33] audit: type=1400 audit(1786540892.743:212): avc: denied { write } for pid=5854 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 114.942742][ T33] audit: type=1400 audit(1786540892.933:213): avc: denied { write } for pid=5857 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.067169][ T33] audit: type=1400 audit(1786540893.063:214): avc: denied { write } for pid=5861 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.222089][ T33] audit: type=1400 audit(1786540893.213:215): avc: denied { write } for pid=5865 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.447584][ T33] audit: type=1400 audit(1786540893.443:216): avc: denied { write } for pid=5870 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.634398][ T33] audit: type=1400 audit(1786540893.633:217): avc: denied { write } for pid=5873 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.722229][ T33] audit: type=1400 audit(1786540893.713:218): avc: denied { write } for pid=5876 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 115.869451][ T33] audit: type=1400 audit(1786540893.863:219): avc: denied { write } for pid=5879 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:56509' (ED25519) to the list of known hosts.
[+] open /dev/kvm successful.
Strace Output: /strace -e \!wait4,clock_nanosleep,nanosleep -s 100 -x -f /syz-executor519858962
<...>
[ 116.266896][ T33] kauditd_printk_skb: 10 callbacks suppressed
[ 116.266911][ T33] audit: type=1400 audit(1786541031.945:201): avc: denied { transition } for pid=5834 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 116.280441][ T33] audit: type=1400 audit(1786541031.945:202): avc: denied { noatsecure } for pid=5834 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 116.288398][ T33] audit: type=1400 audit(1786541031.945:203): avc: denied { rlimitinh } for pid=5834 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 116.298705][ T33] audit: type=1400 audit(1786541031.945:204): avc: denied { siginh } for pid=5834 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 120.332930][ T33] audit: type=1400 audit(1786541036.015:205): avc: denied { write } for pid=5840 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.427959][ T33] audit: type=1400 audit(1786541036.105:206): avc: denied { write } for pid=5843 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.574091][ T33] audit: type=1400 audit(1786541036.245:207): avc: denied { write } for pid=5846 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.666332][ T33] audit: type=1400 audit(1786541036.345:208): avc: denied { write } for pid=5849 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.818953][ T33] audit: type=1400 audit(1786541036.495:209): avc: denied { write } for pid=5852 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.911900][ T33] audit: type=1400 audit(1786541036.595:210): avc: denied { write } for pid=5855 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.309812][ T33] kauditd_printk_skb: 2 callbacks suppressed
[ 121.309828][ T33] audit: type=1400 audit(1786541036.985:213): avc: denied { write } for pid=5864 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.405176][ T33] audit: type=1400 audit(1786541037.085:214): avc: denied { write } for pid=5867 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.710149][ T33] audit: type=1400 audit(1786541037.385:215): avc: denied { write } for pid=5870 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.811771][ T33] audit: type=1400 audit(1786541037.495:216): avc: denied { write } for pid=5873 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.576398][ T33] audit: type=1400 audit(1786541038.255:217): avc: denied { write } for pid=5881 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.719657][ T33] audit: type=1400 audit(1786541038.395:218): avc: denied { write } for pid=5884 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.967984][ T33] audit: type=1400 audit(1786541038.645:219): avc: denied { write } for pid=5888 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 123.079453][ T33] audit: type=1400 audit(1786541038.755:220): avc: denied { write } for pid=5893 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:48211' (ED25519) to the list of known hosts.
execve("/syz-executor519858962", ["/syz-executor519858962"], 0x7ffede00a5f0 /* 11 vars */) = 0
brk(NULL) = 0x555583994000
brk(0x555583994d80) = 0x555583994d80
arch_prctl(ARCH_SET_FS, 0x555583994400) = 0
set_tid_address(0x5555839946d0) = 5910
set_robust_list(0x5555839946e0, 24) = 0
rseq({cpu_id_start=0, cpu_id=RSEQ_CPU_ID_UNINITIALIZED, rseq_cs=NULL, flags=0, node_id=0, mm_cid=0, slice_ctrl={request=0, granted=0, __reserved=0}, __reserved=0}, 33, 0, 0x53053053) = 0
prlimit64(0, RLIMIT_STACK, NULL, {rlim_cur=8192*1024, rlim_max=RLIM64_INFINITY}) = 0
readlinkat(AT_FDCWD, "/proc/self/exe", "/syz-executor519858962", 4096) = 22
getrandom("\x3d\x2d\x47\x7e\x7a\xd7\x3d\xf3", 8, GRND_NONBLOCK) = 8
brk(NULL) = 0x555583994d80
brk(0x5555839b5d80) = 0x5555839b5d80
brk(0x5555839b6000) = 0x5555839b6000
mprotect(0x7f78e0a9b000, 20480, PROT_READ) = 0
[ 125.608544][ T33] audit: type=1400 audit(1786541041.285:221): avc: denied { read write } for pid=5910 comm="syz-executor519" name="kvm" dev="devtmpfs" ino=84 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:kvm_device_t tclass=chr_file permissive=1
openat(AT_FDCWD, "/dev/kvm", O_RDWR) = 3
[ 125.623663][ T33] audit: type=1400 audit(1786541041.295:222): avc: denied { open } for pid=5910 comm="syz-executor519" path="/dev/kvm" dev="devtmpfs" ino=84 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:kvm_device_t tclass=chr_file permissive=1
fstat(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
close(3) = 0
[+] open /dev/kvm successful.
write(1, "[+] open /dev/kvm successful.\n", 30) = 30
exit_group(0) = ?
+++ exited with 0 +++
[ 134.874303][ T1377] ieee802154 phy0 wpan0: encryption failed: -22
[ 134.881697][ T1377] ieee802154 phy1 wpan1: encryption failed: -22
Crash Report:
|
| 75/4 |
2026/08/12 13:24 |
llm |
repro-oracle |
0m
Model:
Tokens:
input: 15178
output: 59
thoughts: 272
Thoughts: **Analyzing the Capability Probe Results**
My primary objective here is to meticulously analyze the output of a capability probe program. This particular probe was specifically engineered to ascertain the accessibility of `/dev/kvm`. I've reviewed the provided output, and it clearly indicates success: `[+] open /dev/kvm successful.` Furthermore, the program terminated cleanly with an exit code of 0, which is a strong indicator of a favorable outcome.
Considering the parameters of this probe, I'm also noting the `IsProbe` flag, which is confirmed to be true, as expected for this diagnostic run. Given that the probe for `/dev/kvm` passed without issue, I can confidently assert that the `TerminalError` field should be empty. Consequently, the `ProbePassed` flag must be set to `true`.
Another crucial observation is that there was no crash or unexpected termination that might indicate a vulnerability. This means the `TitleMatches` flag should remain `false`.
Based on this comprehensive assessment, my feedback to the user will be direct and actionable. I need to communicate that the environment is fully prepared, specifically that `/dev/kvm` is accessible, and therefore, the agent should now proceed to generate the complete reproducer in the subsequent stage.
To confirm my understanding, I've re-examined the raw output, specifically the lines related to `write` and `exit_group(0)`. This reiterates my conclusion that the probe executed successfully.
Therefore, I will be invoking the `set-results` command with the following parameters:
* `ProbePassed`: `true`
* `TerminalError`: `""`
* `TitleMatches`: `false`
* `Feedback`: "The environment probe was successful. `/dev/kvm` is accessible. Please proceed to generate the full reproducer in the next iteration."
|
| 76/4 |
2026/08/12 13:24 |
tool |
set-results |
0m
Args: map[Feedback:The environment probe was successful. `/dev/kvm` is accessible. Please proceed to generate the full reproducer in the next iteration. ProbePassed:true TerminalError: TitleMatches:false]
Results: map[Feedback:The environment probe was successful. `/dev/kvm` is accessible. Please proceed to generate the full reproducer in the next iteration. ProbePassed:true TerminalError: TitleMatches:false]
|
| 77/3 |
2026/08/12 13:24 |
action |
loop-controller |
0m
Results: map[CapabilitiesVerified:true ContinueSignal:continue EquivalenceAnalysis: OracleFeedback:The environment probe was successful. `/dev/kvm` is accessible. Please proceed to generate the full reproducer in the next iteration. ReproC: Reproduced:false ReproducedBugTitle: ReproducedCrashReport:]
|
| 78/2 |
2026/08/12 13:24 |
iteration |
1 |
5m
|
| 79/3 |
2026/08/12 13:24 |
action |
If |
1m
Args: map[OracleFeedback:The environment probe was successful. `/dev/kvm` is accessible. Please proceed to generate the full reproducer in the next iteration.]
|
| 80/4 |
2026/08/12 13:24 |
agent |
strategy-refiner |
1m
Model:
Instruction: You are an expert in Linux kernel debugging.
Refine the reproduction strategy based on feedback from previous attempts.
Analyze the technical diagnosis provided in the oracle feedback and translate it into concrete,
step-by-step instructions for the repro-generator on how to modify the code structure, alignments,
offsets, or parameters of the candidate program.
=== TOOL SELECTION GUIDELINES ===
- Prefer codesearch-definition-source and codesearch-struct-layout first for symbol lookups.
- Fall back to read-file or grepper for macros, headers, or if symbol lookup fails.
=== CRITICAL PROHIBITIONS ===
- Do NOT repeat searches for the same symbols or files. Use information you have already gathered.
- Do NOT write long explanations. Keep your reasoning short and focused on actionable changes.
- Do NOT assume a bug is fixed based on git commit history.
- If you are stuck, try a different approach or proceed to generate a candidate reproducer.
Prefer calling several tools at the same time to save round-trips.
Prompt: Bug Description: BUG: sleeping function called from invalid context in kvm_xen_set_evtchn_fast
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:248
in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 5622, name: syz-executor363
preempt_count: 10000, expected: 0
RCU nest depth: 1, expected: 1
locks held by syz-executor363/5622: 4, last CPU#0:
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: __simple_recursive_removal+0x19a/0x520 fs/libfs.c:619
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
#2: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rtlock_slowlock_locked+0x2ab/0x3c20 kernel/locking/rtmutex.c:1874
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1be/0x990 arch/x86/kvm/xen.c:1827
irq event stamp: 13272
hardirqs last enabled at (13271): [<ffffffff8b53b4b3>] __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:187 [inline]
hardirqs last enabled at (13271): [<ffffffff8b53b4b3>] _raw_spin_unlock_irq+0x23/0x50 kernel/locking/spinlock.c:206
hardirqs last disabled at (13272): [<ffffffff8b501aee>] sysvec_apic_timer_interrupt+0xe/0xc0 arch/x86/kernel/apic/apic.c:1062
softirqs last enabled at (6940): [<ffffffff81882fe0>] __local_bh_enable_ip+0x1a0/0x2b0 kernel/softirq.c:305
softirqs last disabled at (6932): [<ffffffff891cda09>] local_bh_disable include/linux/bottom_half.h:20 [inline]
softirqs last disabled at (6932): [<ffffffff891cda09>] __alloc_skb+0x189/0x7a0 net/core/skbuff.c:697
Preemption disabled at:
[<ffffffff81883b8e>] irq_enter_rcu+0x1e/0x1f0 kernel/softirq.c:668
CPU: 0 UID: 0 PID: 5622 Comm: syz-executor363 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
__might_resched+0x329/0x480 kernel/sched/core.c:9194
rt_read_lock+0xa9/0x4b0 kernel/locking/spinlock_rt.c:248
kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x3a0/0xaf0 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x44a/0x900 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:rt_mutex_owner include/linux/rtmutex.h:52 [inline]
RIP: 0010:rtmutex_spin_on_owner kernel/locking/rtmutex.c:1504 [inline]
RIP: 0010:rtlock_slowlock_locked+0x34e5/0x3c20 kernel/locking/rtmutex.c:1893
Code: 80 3c 01 00 4c 8b b4 24 80 00 00 00 4c 8b 2c 24 74 08 4c 89 ef e8 db 0e df f6 48 8d 84 24 60 01 00 00 49 39 45 00 75 6c f3 90 <48> b8 00 00 00 00 00 fc ff df 48 8b 8c 24 a8 00 00 00 80 3c 01 00
RSP: 0018:ffffc90004e6f7a0 EFLAGS: 00000246
RAX: ffffc90004e6f900 RBX: 1ffff11006ff9bbe RCX: 1ffffffff1ca7871
RDX: 00000000e6b90d15 RSI: ffffffff8bcbd060 RDI: 0000000000000001
RBP: ffffc90004e6f9f0 R08: 1d00000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8e3c3880 R12: ffff888037fcddc0
R13: ffffffff8e53c388 R14: ffffffff8e53c390 R15: 1ffff11006ff9bba
rtlock_slowlock kernel/locking/rtmutex.c:1922 [inline]
rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
__rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
rt_spin_lock+0x165/0x400 kernel/locking/spinlock_rt.c:57
spin_lock include/linux/spinlock_rt.h:45 [inline]
simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
__simple_recursive_removal+0x215/0x520 fs/libfs.c:623
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:781
kvm_destroy_vm_debugfs virt/kvm/kvm_main.c:988 [inline]
kvm_destroy_vm virt/kvm/kvm_main.c:1261 [inline]
kvm_put_kvm+0x147/0xae0 virt/kvm/kvm_main.c:1331
kvm_vm_release+0x46/0x50 virt/kvm/kvm_main.c:1354
__fput+0x42a/0xa80 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x73a/0x2360 kernel/exit.c:1009
do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
__do_sys_exit_group kernel/exit.c:1163 [inline]
__se_sys_exit_group kernel/exit.c:1161 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1161
x64_sys_call+0x18bf/0x18c0 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f132ec60d05
Code: Unable to access opcode bytes at 0x7f132ec60cdb.
RSP: 002b:00007ffe413e3968 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f132ec60d05
RDX: 00000000000000e7 RSI: ffffffffffffffd8 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000009 R11: 0000000000000202 R12: 0000000000000000
R13: 00007f132ecfa118 R14: 00007f132ecfc3c8 R15: 00007f132ecfc3e0
</TASK>
=============================
[ BUG: Invalid wait context ]
syzkaller #0 Tainted: G W
-----------------------------
syz-executor363/5622 is trying to lock:
ffff888038241530 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
other info that might help us debug this:
context-{2:2}
locks held by syz-executor363/5622: 4, last CPU#0:
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: __simple_recursive_removal+0x19a/0x520 fs/libfs.c:619
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
#2: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rtlock_slowlock_locked+0x2ab/0x3c20 kernel/locking/rtmutex.c:1874
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1be/0x990 arch/x86/kvm/xen.c:1827
stack backtrace:
CPU: 0 UID: 0 PID: 5622 Comm: syz-executor363 Tainted: G W syzkaller #0 PREEMPT_{RT,(full)}
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_lock_invalid_wait_context kernel/locking/lockdep.c:4846 [inline]
check_wait_context kernel/locking/lockdep.c:4918 [inline]
__lock_acquire+0xef0/0x2e40 kernel/locking/lockdep.c:5204
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5906
rt_read_lock+0xcc/0x4b0 kernel/locking/spinlock_rt.c:249
kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x3a0/0xaf0 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x44a/0x900 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:rt_mutex_owner include/linux/rtmutex.h:52 [inline]
RIP: 0010:rtmutex_spin_on_owner kernel/locking/rtmutex.c:1504 [inline]
RIP: 0010:rtlock_slowlock_locked+0x34e5/0x3c20 kernel/locking/rtmutex.c:1893
Code: 80 3c 01 00 4c 8b b4 24 80 00 00 00 4c 8b 2c 24 74 08 4c 89 ef e8 db 0e df f6 48 8d 84 24 60 01 00 00 49 39 45 00 75 6c f3 90 <48> b8 00 00 00 00 00 fc ff df 48 8b 8c 24 a8 00 00 00 80 3c 01 00
RSP: 0018:ffffc90004e6f7a0 EFLAGS: 00000246
RAX: ffffc90004e6f900 RBX: 1ffff11006ff9bbe RCX: 1ffffffff1ca7871
RDX: 00000000e6b90d15 RSI: ffffffff8bcbd060 RDI: 0000000000000001
RBP: ffffc90004e6f9f0 R08: 1d00000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8e3c3880 R12: ffff888037fcddc0
R13: ffffffff8e53c388 R14: ffffffff8e53c390 R15: 1ffff11006ff9bba
rtlock_slowlock kernel/locking/rtmutex.c:1922 [inline]
rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
__rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
rt_spin_lock+0x165/0x400 kernel/locking/spinlock_rt.c:57
spin_lock include/linux/spinlock_rt.h:45 [inline]
simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
__simple_recursive_removal+0x215/0x520 fs/libfs.c:623
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:781
kvm_destroy_vm_debugfs virt/kvm/kvm_main.c:988 [inline]
kvm_destroy_vm virt/kvm/kvm_main.c:1261 [inline]
kvm_put_kvm+0x147/0xae0 virt/kvm/kvm_main.c:1331
kvm_vm_release+0x46/0x50 virt/kvm/kvm_main.c:1354
__fput+0x42a/0xa80 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x73a/0x2360 kernel/exit.c:1009
do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
__do_sys_exit_group kernel/exit.c:1163 [inline]
__se_sys_exit_group kernel/exit.c:1161 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1161
x64_sys_call+0x18bf/0x18c0 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f132ec60d05
Code: Unable to access opcode bytes at 0x7f132ec60cdb.
RSP: 002b:00007ffe413e3968 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f132ec60d05
RDX: 00000000000000e7 RSI: ffffffffffffffd8 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000009 R11: 0000000000000202 R12: 0000000000000000
R13: 00007f132ecfa118 R14: 00007f132ecfc3c8 R15: 00007f132ecfc3e0
</TASK>
----------------
Code disassembly (best guess):
0: 80 3c 01 00 cmpb $0x0,(%rcx,%rax,1)
4: 4c 8b b4 24 80 00 00 mov 0x80(%rsp),%r14
b: 00
c: 4c 8b 2c 24 mov (%rsp),%r13
10: 74 08 je 0x1a
12: 4c 89 ef mov %r13,%rdi
15: e8 db 0e df f6 call 0xf6df0ef5
1a: 48 8d 84 24 60 01 00 lea 0x160(%rsp),%rax
21: 00
22: 49 39 45 00 cmp %rax,0x0(%r13)
26: 75 6c jne 0x94
28: f3 90 pause
* 2a: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax <-- trapping instruction
31: fc ff df
34: 48 8b 8c 24 a8 00 00 mov 0xa8(%rsp),%rcx
3b: 00
3c: 80 3c 01 00 cmpb $0x0,(%rcx,%rax,1)
Current Strategy: An analysis of the bug report reveals that this is a PREEMPT_RT specific issue in the KVM Xen emulation code.
### Bug Analysis
1. **Context**: The bug is a "sleeping function called from invalid context" which occurs in a kernel compiled with `CONFIG_PREEMPT_RT`.
2. **Trigger**: The stack trace shows that the high-resolution timer callback `xen_timer_callback()` executes in hardirq context (as it is armed with `HRTIMER_MODE_ABS_HARD`).
3. **Root Cause**: `xen_timer_callback()` calls `kvm_xen_set_evtchn_fast()`, which unconditionally attempts to acquire a read lock on `gpc->lock` (a `rwlock_t`) via `read_lock_irqsave()`. In PREEMPT_RT kernels, `rwlock_t` is mapped to a sleeping lock (`rt_read_lock`). Acquiring a sleeping lock in hardirq context is invalid and triggers the BUG.
4. **Path to Reproduce**: We can trigger this by simply creating a KVM VM and VCPU, and then using the `KVM_XEN_VCPU_SET_ATTR` ioctl to arm the Xen timer (`KVM_XEN_VCPU_ATTR_TYPE_TIMER`). If we set the timer expiration to a short time in the future, `kvm_xen_start_timer()` will arm the hrtimer asynchronously. When the timer expires, it fires in hardirq context and hits the invalid lock acquisition.
### Reproduction Strategy
We can reproduce this issue with a minimal C program that:
1. Opens `/dev/kvm` and creates a VM and a VCPU.
2. Calls the `KVM_XEN_VCPU_SET_ATTR` ioctl on the VCPU to set up a Xen timer.
3. Sets the timer's `expires_ns` to a value safely in the future (e.g., 1 second) to ensure the timer is armed asynchronously rather than firing synchronously during the ioctl.
4. Sleeps to allow the timer to expire and trigger the bug in the interrupt context.
### Minimal C Reproducer
```c
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
/* Define KVM Xen constants in case they are missing from older headers */
#ifndef KVM_XEN_VCPU_ATTR_TYPE_TIMER
#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
#endif
#ifndef KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL
#define KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL ((uint32_t)(-1))
#endif
/* Local definition of the attribute struct to ensure compilation */
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
#define MY_KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
int main(void)
{
int kvm_fd, vm_fd, vcpu_fd;
struct my_kvm_xen_vcpu_attr attr = {0};
kvm_fd = open("/dev/kvm", O_RDWR);
if (kvm_fd < 0) {
perror("open /dev/kvm");
return 1;
}
vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0);
if (vm_fd < 0) {
perror("KVM_CREATE_VM");
return 1;
}
vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);
if (vcpu_fd < 0) {
perror("KVM_CREATE_VCPU");
return 1;
}
/*
* Arm the Xen timer.
* The guest kvmclock starts at 0 when the VM is created.
* Setting expires_ns to 1 second ensures delta > 0, forcing
* the hrtimer to be armed asynchronously.
*/
attr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
attr.u.timer.port = 1;
attr.u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
attr.u.timer.expires_ns = 1000000000ULL; /* 1 second */
if (ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr) < 0) {
perror("KVM_XEN_VCPU_SET_ATTR");
return 1;
}
/* Wait for the hrtimer to fire in hardirq context */
sleep(2);
return 0;
}
```
Feedback: The environment probe was successful. `/dev/kvm` is accessible. Please proceed to generate the full reproducer in the next iteration.
Reply: The environment probe confirms that `/dev/kvm` is accessible and the basic KVM setup works. We can now proceed to generate the full C reproducer.
### Bug Analysis
The bug is a "sleeping function called from invalid context" in `kvm_xen_set_evtchn_fast()`, which occurs on `PREEMPT_RT` kernels.
1. The Xen timer is armed via the `KVM_XEN_VCPU_SET_ATTR` ioctl.
2. If the timer's expiration time is in the future, KVM arms an asynchronous hrtimer (`HRTIMER_MODE_ABS_HARD`).
3. When the timer expires, `xen_timer_callback()` executes in **hardirq context**.
4. The callback invokes `kvm_xen_set_evtchn_fast()`, which attempts to acquire `gpc->lock` (a `rwlock_t`).
5. On `PREEMPT_RT`, `rwlock_t` is mapped to a sleeping lock (`rt_rw_lock`). Acquiring a sleeping lock in hardirq context is invalid and triggers the BUG.
### Reproduction Strategy
To trigger the bug, we just need to arm the Xen timer with an expiration time safely in the future (e.g., 1 second) so that it fires asynchronously in hardirq context.
Please generate the C reproducer using the following step-by-step instructions:
1. **Include Headers**: Include `<fcntl.h>`, `<sys/ioctl.h>`, `<linux/kvm.h>`, `<stdint.h>`, `<unistd.h>`, and `<stdio.h>`.
2. **Define Constants**: Define `KVM_XEN_VCPU_ATTR_TYPE_TIMER` as `0x7` and `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL` as `((uint32_t)(-1))` to ensure compatibility with older headers.
3. **Define Attribute Struct**: Define a local version of the Xen VCPU attribute struct to avoid missing definitions in older kernel headers:
```c
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
#define MY_KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
```
4. **KVM Setup**: In `main()`, open `/dev/kvm`, create a VM (`KVM_CREATE_VM`), and create a VCPU (`KVM_CREATE_VCPU`).
5. **Arm the Timer**:
- Initialize the `my_kvm_xen_vcpu_attr` struct to zero.
- Set `type` to `KVM_XEN_VCPU_ATTR_TYPE_TIMER`.
- Set `u.timer.port` to `1`.
- Set `u.timer.priority` to `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL`.
- Set `u.timer.expires_ns` to `1000000000ULL` (1 second).
- Call `ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr)`.
6. **Wait for Execution**: Add `sleep(2);` at the end of `main()` to keep the process alive long enough for the hrtimer to fire in the background and trigger the bug.
|
| 81/5 |
2026/08/12 13:24 |
llm |
strategy-refiner |
0m
Model:
Tokens:
input: 10215
output: 41
thoughts: 859
Thoughts: **My Thought Process on Refining the Bug Reproduction Strategy**
Alright, let's break down what's going on with this "BUG: sleeping function called from invalid context in kvm_xen_set_evtchn_fast" issue. My primary objective here is to create a precise and effective reproduction strategy, translating the technical analysis into actionable instructions for the repro-generator.
First, I've identified the core problem: `kvm_xen_set_evtchn_fast` is being invoked from `xen_timer_callback`. The critical detail is that `xen_timer_callback` operates within a hardirq context due to it being an hrtimer callback. This is where the conflict arises, as `kvm_xen_set_evtchn_fast` attempts to acquire locks that are sleeping locks when PREEMPT_RT is enabled, or `srcu_read_lock`.
Looking at the provided stack traces is crucial. I see two key locking attempts within `kvm_xen_set_evtchn_fast`:
1. It's trying to acquire `gpc->lock`, identified as a `rwlock_t`. The trace confirms this attempt at `kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829`.
2. Simultaneously, it's attempting to acquire `kvm->srcu` via `srcu_read_lock` at `kvm_xen_set_evtchn_fast+0x1be/0x990 arch/x86/kvm/xen.c:1827`.
The fact that these are sleeping locks in a hardirq context is the direct cause of the bug.
Now, the user has provided a C reproducer in the "Current Strategy" section, and the feedback indicates that the environment probe was successful, with `/dev/kvm` being accessible. The next step, as per the prompt, is to refine this reproduction strategy into concrete instructions for the repro-generator.
I need to scrutinize the provided C code snippet to see if any modifications are necessary to specifically trigger this bug reliably. The relevant part is:
```c
/*
* Arm the Xen timer.
* The guest kvmclock starts at 0 when the VM is created.
* Setting expires_ns to 1 second ensures delta > 0, forcing
* the hrtimer to be armed asynchronously.
*/
attr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
attr.u.timer.port = 1;
attr.u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
attr.u.timer.expires_ns = 1000000000ULL; /* 1 second */
```
The comment here is insightful. It suggests that setting `expires_ns` to a value greater than zero ensures the hrtimer is armed asynchronously. The bug occurs because `kvm_xen_set_evtchn_fast` is called from `xen_timer_callback` *if* `vcpu->arch.xen.timer.port` is set. The provided code snippet *is* setting `attr.u.timer.port = 1`, which directly enables this path.
Therefore, the current C code seems to be on the right track for triggering the scenario where `kvm_xen_set_evtchn_fast` is called from the timer callback. My task is to translate this understanding into instructions for the repro-generator. I don't see a need to alter the *structure*, *alignments*, or *offsets* of the candidate program itself based on this analysis; rather, the focus is on ensuring the *parameters* and the *execution flow* precisely match the problematic path identified.
So, the instructions should focus on ensuring the specific KVM ioctls and parameters are used to set up the Xen timer in a way that guarantees `xen_timer_callback` is triggered while `kvm_xen_set_evtchn_fast` is called within it. The provided C snippet already does this by setting `KVM_XEN_VCPU_ATTR_TYPE_TIMER` and providing a non-zero `port` and `expires_ns`.
Essentially, the repro-generator needs to implement the sequence of system calls that leads to this state. This includes:
* Opening `/dev/kvm`.
* Creating a VM.
* Creating a vCPU.
* Setting the Xen VCPU attributes as shown in the snippet, specifically focusing on `KVM_XEN_VCPU_ATTR_TYPE_TIMER`, `port = 1`, and `expires_ns = 1000000000ULL`.
* Ensuring the system is configured with PREEMPT_RT enabled, as this is where the sleeping lock behavior becomes problematic.
The provided C code seems to be a good starting point for the *logic* to trigger the bug. My instructions will be to ensure this logic is robustly implemented within the generator's framework.
|
| 82/5 |
2026/08/12 13:24 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c Name:xen_timer_callback]
Results: map[SourceCode: 126: static enum hrtimer_restart xen_timer_callback(struct hrtimer *timer)
127: {
128: struct kvm_vcpu *vcpu = container_of(timer, struct kvm_vcpu,
129: arch.xen.timer);
130: struct kvm_xen_evtchn e;
131: int rc;
132:
133: if (atomic_read(&vcpu->arch.xen.timer_pending))
134: return HRTIMER_NORESTART;
135:
136: e.vcpu_id = vcpu->vcpu_id;
137: e.vcpu_idx = vcpu->vcpu_idx;
138: e.port = vcpu->arch.xen.timer_virq;
139: e.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
140:
141: rc = kvm_xen_set_evtchn_fast(&e, vcpu->kvm);
142: if (rc != -EWOULDBLOCK) {
143: vcpu->arch.xen.timer_expires = 0;
144: return HRTIMER_NORESTART;
145: }
146:
147: atomic_inc(&vcpu->arch.xen.timer_pending);
148: kvm_make_request(KVM_REQ_UNBLOCK, vcpu);
149: kvm_vcpu_kick(vcpu);
150:
151: return HRTIMER_NORESTART;
152: }
SourceFile:arch/x86/kvm/xen.c]
|
| 83/5 |
2026/08/12 13:24 |
llm |
strategy-refiner |
0m
Model:
Tokens:
input: 11587
output: 62
thoughts: 45
Thoughts: **My Thought Process Regarding Timer Virq Initialization**
So, I've just encountered this line: `e.port = vcpu->arch.xen.timer_virq;`. My immediate thought is, "Okay, I'm assigning a port value." But then, my brain kicks in with a critical follow-up: "Hold on a second, what *is* `timer_virq` and how did it get its value?" This is the crucial point of inquiry because, without knowing its origin and how it's populated, this assignment is essentially meaningless, or worse, could be based on faulty data. Therefore, my immediate next step in this thought process is to delve into the mechanism that *sets* `timer_virq`. I need to trace back how this specific value, which is clearly important for timer virtualization in this Xen context, is initialized and updated throughout the system.
|
| 84/5 |
2026/08/12 13:24 |
tool |
codesearch-find-references |
0m
Error:
Args: map[ContextFile:arch/x86/kvm/xen.c IncludeSnippetLines:2 Name:timer_virq SourceTreePrefix:arch/x86/kvm/]
Results: map[References:<nil> TruncatedOutput:false]
|
| 85/5 |
2026/08/12 13:24 |
llm |
strategy-refiner |
0m
Model:
Tokens:
input: 11693
output: 36
thoughts: 46
Thoughts: **My Thought Process on KVM and Xen Integration**
Ah, I see. My immediate focus shifts to a specific detail: the `struct kvm_vcpu_arch.xen` field. This tells me I'm deep in the weeds of how KVM (Kernel-based Virtual Machine) interacts with Xen, the hypervisor. It's not just a general KVM inquiry; it's about the architectural specifics of the Xen integration.
My next logical step, given this architectural context, is to investigate how timers are handled within this KVM-Xen setup. The mention of `timer_virq` strongly suggests a Virtual IRQ (Interrupt Request) related to timer events. Virtual IRQs are fundamental to virtualization, representing interrupts from the guest's perspective, but managed by the hypervisor.
Therefore, my thought process leads me directly to searching for `timer_virq` within the `arch/x86/kvm/xen.c` file. This is the most direct route to understanding how KVM, on an x86 architecture, implements Xen-specific timer virtualization. I'm expecting to find code that:
* Defines or uses the `timer_virq` identifier.
* Handles the injection of timer interrupts into the guest VM when running under Xen.
* Potentially details the interaction between KVM's timer management and Xen's own timer mechanisms.
* Explains how KVM exposes or emulates Xen's timer events to the virtual CPU.
This targeted search is crucial for understanding the low-level mechanics of timer virtualization in this specific KVM-Xen scenario, allowing me to pinpoint the precise implementation details.
|
| 86/5 |
2026/08/12 13:24 |
tool |
grepper |
0m
Args: map[Expression:timer_virq PathPrefix:arch/x86/kvm/xen.c]
Results: map[Output:arch/x86/kvm/xen.c=109=void kvm_xen_inject_timer_irqs(struct kvm_vcpu *vcpu)
--
arch/x86/kvm/xen.c-115- e.vcpu_idx = vcpu->vcpu_idx;
arch/x86/kvm/xen.c:116: e.port = vcpu->arch.xen.timer_virq;
arch/x86/kvm/xen.c-117- e.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
--
arch/x86/kvm/xen.c=126=static enum hrtimer_restart xen_timer_callback(struct hrtimer *timer)
--
arch/x86/kvm/xen.c-137- e.vcpu_idx = vcpu->vcpu_idx;
arch/x86/kvm/xen.c:138: e.port = vcpu->arch.xen.timer_virq;
arch/x86/kvm/xen.c-139- e.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
--
arch/x86/kvm/xen.c=907=int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
--
arch/x86/kvm/xen.c-1125- kvm_xen_stop_timer(vcpu);
arch/x86/kvm/xen.c:1126: vcpu->arch.xen.timer_virq = data->u.timer.port;
arch/x86/kvm/xen.c-1127-
--
arch/x86/kvm/xen.c=1153=int kvm_xen_vcpu_get_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
--
arch/x86/kvm/xen.c-1246-
arch/x86/kvm/xen.c:1247: data->u.timer.port = vcpu->arch.xen.timer_virq;
arch/x86/kvm/xen.c-1248- data->u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
]
|
| 87/5 |
2026/08/12 13:24 |
llm |
strategy-refiner |
0m
Model:
Tokens:
input: 12401
output: 47
thoughts: 96
Thoughts: **My Thought Process Regarding KVM Xen Timer Configuration**
Alright, so my initial observation is that the assignment `vcpu->arch.xen.timer_virq = data->u.timer.port;` is taking place within the `kvm_xen_vcpu_set_attr` function. This assignment specifically happens when the `data->type` field is equal to `KVM_XEN_VCPU_ATTR_TYPE_TIMER`.
Given this, my immediate next step in my investigation is to delve into the `kvm_xen_vcpu_set_attr` function and meticulously examine the code path that handles the `KVM_XEN_VCPU_ATTR_TYPE_TIMER` case. I need to understand precisely *how* and *why* that `timer_virq` value, sourced from `data->u.timer.port`, is being utilized in the context of KVM's Xen integration. This will likely involve tracing the flow of execution from that point onwards to see what Xen-specific timer operations are being enabled or configured based on this attribute.
|
| 88/5 |
2026/08/12 13:24 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c Name:kvm_xen_vcpu_set_attr]
Results: map[SourceCode: 907: int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
908: {
909: int idx, r = -ENOENT;
910:
911: mutex_lock(&vcpu->kvm->arch.xen.xen_lock);
912: idx = srcu_read_lock(&vcpu->kvm->srcu);
913:
914: switch (data->type) {
915: case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO:
916: case KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO_HVA:
917: /* No compat necessary here. */
918: BUILD_BUG_ON(sizeof(struct vcpu_info) !=
919: sizeof(struct compat_vcpu_info));
920: BUILD_BUG_ON(offsetof(struct vcpu_info, time) !=
921: offsetof(struct compat_vcpu_info, time));
922:
923: if (data->type == KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO) {
924: if (data->u.gpa == KVM_XEN_INVALID_GPA) {
925: kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
926: r = 0;
927: break;
928: }
929:
930: r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_info_cache,
931: data->u.gpa, sizeof(struct vcpu_info));
932: } else {
933: if (data->u.hva == 0) {
934: kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_info_cache);
935: r = 0;
936: break;
937: }
938:
939: r = kvm_gpc_activate_hva(&vcpu->arch.xen.vcpu_info_cache,
940: data->u.hva, sizeof(struct vcpu_info));
941: }
942:
943: if (!r)
944: kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
945:
946: break;
947:
948: case KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO:
949: if (data->u.gpa == KVM_XEN_INVALID_GPA) {
950: kvm_gpc_deactivate(&vcpu->arch.xen.vcpu_time_info_cache);
951: r = 0;
952: break;
953: }
954:
955: r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_time_info_cache,
956: data->u.gpa,
957: sizeof(struct pvclock_vcpu_time_info));
958: if (!r)
959: kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
960: break;
961:
962: case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADDR: {
963: size_t sz, sz1, sz2;
964:
965: if (!sched_info_on()) {
966: r = -EOPNOTSUPP;
967: break;
968: }
969: if (data->u.gpa == KVM_XEN_INVALID_GPA) {
970: r = 0;
971: deactivate_out:
972: kvm_gpc_deactivate(&vcpu->arch.xen.runstate_cache);
973: kvm_gpc_deactivate(&vcpu->arch.xen.runstate2_cache);
974: break;
975: }
976:
977: /*
978: * If the guest switches to 64-bit mode after setting the runstate
979: * address, that's actually OK. kvm_xen_update_runstate_guest()
980: * will cope.
981: */
982: if (IS_ENABLED(CONFIG_64BIT) && vcpu->kvm->arch.xen.long_mode)
983: sz = sizeof(struct vcpu_runstate_info);
984: else
985: sz = sizeof(struct compat_vcpu_runstate_info);
986:
987: /* How much fits in the (first) page? */
988: sz1 = PAGE_SIZE - (data->u.gpa & ~PAGE_MASK);
989: r = kvm_gpc_activate(&vcpu->arch.xen.runstate_cache,
990: data->u.gpa, sz1);
991: if (r)
992: goto deactivate_out;
993:
994: /* Either map the second page, or deactivate the second GPC */
995: if (sz1 >= sz) {
996: kvm_gpc_deactivate(&vcpu->arch.xen.runstate2_cache);
997: } else {
998: sz2 = sz - sz1;
999: BUG_ON((data->u.gpa + sz1) & ~PAGE_MASK);
1000: r = kvm_gpc_activate(&vcpu->arch.xen.runstate2_cache,
1001: data->u.gpa + sz1, sz2);
1002: if (r)
1003: goto deactivate_out;
1004: }
1005:
1006: kvm_xen_update_runstate_guest(vcpu, false);
1007: break;
1008: }
1009: case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_CURRENT:
1010: if (!sched_info_on()) {
1011: r = -EOPNOTSUPP;
1012: break;
1013: }
1014: if (data->u.runstate.state > RUNSTATE_offline) {
1015: r = -EINVAL;
1016: break;
1017: }
1018:
1019: kvm_xen_update_runstate(vcpu, data->u.runstate.state);
1020: r = 0;
1021: break;
1022:
1023: case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_DATA:
1024: if (!sched_info_on()) {
1025: r = -EOPNOTSUPP;
1026: break;
1027: }
1028: if (data->u.runstate.state > RUNSTATE_offline) {
1029: r = -EINVAL;
1030: break;
1031: }
1032: if (data->u.runstate.state_entry_time !=
1033: (data->u.runstate.time_running +
1034: data->u.runstate.time_runnable +
1035: data->u.runstate.time_blocked +
1036: data->u.runstate.time_offline)) {
1037: r = -EINVAL;
1038: break;
1039: }
1040: if (get_kvmclock_ns(vcpu->kvm) <
1041: data->u.runstate.state_entry_time) {
1042: r = -EINVAL;
1043: break;
1044: }
1045:
1046: vcpu->arch.xen.current_runstate = data->u.runstate.state;
1047: vcpu->arch.xen.runstate_entry_time =
1048: data->u.runstate.state_entry_time;
1049: vcpu->arch.xen.runstate_times[RUNSTATE_running] =
1050: data->u.runstate.time_running;
1051: vcpu->arch.xen.runstate_times[RUNSTATE_runnable] =
1052: data->u.runstate.time_runnable;
1053: vcpu->arch.xen.runstate_times[RUNSTATE_blocked] =
1054: data->u.runstate.time_blocked;
1055: vcpu->arch.xen.runstate_times[RUNSTATE_offline] =
1056: data->u.runstate.time_offline;
1057: vcpu->arch.xen.last_steal = current->sched_info.run_delay;
1058: r = 0;
1059: break;
1060:
1061: case KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST:
1062: if (!sched_info_on()) {
1063: r = -EOPNOTSUPP;
1064: break;
1065: }
1066: if (data->u.runstate.state > RUNSTATE_offline &&
1067: data->u.runstate.state != (u64)-1) {
1068: r = -EINVAL;
1069: break;
1070: }
1071: /* The adjustment must add up */
1072: if (data->u.runstate.state_entry_time !=
1073: (data->u.runstate.time_running +
1074: data->u.runstate.time_runnable +
1075: data->u.runstate.time_blocked +
1076: data->u.runstate.time_offline)) {
1077: r = -EINVAL;
1078: break;
1079: }
1080:
1081: if (get_kvmclock_ns(vcpu->kvm) <
1082: (vcpu->arch.xen.runstate_entry_time +
1083: data->u.runstate.state_entry_time)) {
1084: r = -EINVAL;
1085: break;
1086: }
1087:
1088: vcpu->arch.xen.runstate_entry_time +=
1089: data->u.runstate.state_entry_time;
1090: vcpu->arch.xen.runstate_times[RUNSTATE_running] +=
1091: data->u.runstate.time_running;
1092: vcpu->arch.xen.runstate_times[RUNSTATE_runnable] +=
1093: data->u.runstate.time_runnable;
1094: vcpu->arch.xen.runstate_times[RUNSTATE_blocked] +=
1095: data->u.runstate.time_blocked;
1096: vcpu->arch.xen.runstate_times[RUNSTATE_offline] +=
1097: data->u.runstate.time_offline;
1098:
1099: if (data->u.runstate.state <= RUNSTATE_offline)
1100: kvm_xen_update_runstate(vcpu, data->u.runstate.state);
1101: else if (vcpu->arch.xen.runstate_cache.active)
1102: kvm_xen_update_runstate_guest(vcpu, false);
1103: r = 0;
1104: break;
1105:
1106: case KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID:
1107: BUILD_BUG_ON(XEN_VCPU_ID_INVALID < KVM_MAX_VCPUS);
1108:
1109: if (data->u.vcpu_id >= KVM_MAX_VCPUS)
1110: r = -EINVAL;
1111: else {
1112: vcpu->arch.xen.vcpu_id = data->u.vcpu_id;
1113: r = 0;
1114: }
1115: break;
1116:
1117: case KVM_XEN_VCPU_ATTR_TYPE_TIMER:
1118: if (data->u.timer.port &&
1119: data->u.timer.priority != KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL) {
1120: r = -EINVAL;
1121: break;
1122: }
1123:
1124: /* Stop the timer (if it's running) before changing the vector */
1125: kvm_xen_stop_timer(vcpu);
1126: vcpu->arch.xen.timer_virq = data->u.timer.port;
1127:
1128: /* Start the timer if the new value has a valid vector+expiry. */
1129: if (data->u.timer.port && data->u.timer.expires_ns)
1130: kvm_xen_start_timer(vcpu, data->u.timer.expires_ns, false);
1131:
1132: r = 0;
1133: break;
1134:
1135: case KVM_XEN_VCPU_ATTR_TYPE_UPCALL_VECTOR:
1136: if (data->u.vector && data->u.vector < 0x10)
1137: r = -EINVAL;
1138: else {
1139: vcpu->arch.xen.upcall_vector = data->u.vector;
1140: r = 0;
1141: }
1142: break;
1143:
1144: default:
1145: break;
1146: }
1147:
1148: srcu_read_unlock(&vcpu->kvm->srcu, idx);
1149: mutex_unlock(&vcpu->kvm->arch.xen.xen_lock);
1150: return r;
1151: }
SourceFile:arch/x86/kvm/xen.c]
|
| 89/5 |
2026/08/12 13:24 |
llm |
strategy-refiner |
0m
Model:
Tokens:
input: 16608
output: 47
thoughts: 790
Thoughts: **My Thought Process Unraveling the KVM Xen Event Channel Bug**
Okay, let me walk you through my thinking on this KVM Xen event channel issue. Initially, I was looking at `kvm_xen_vcpu_set_attr` as the potential culprit because it's involved in setting up timers and starting them. That seemed like a plausible entry point for a timer-related bug.
However, as I delved deeper into the stack trace and the reported bug, my focus shifted. The actual bug manifests within `kvm_xen_set_evtchn_fast`, and crucially, this function is invoked via the `xen_timer_callback`. This immediately told me the problem wasn't in the initial timer setup itself, but rather in how the Xen event channel mechanism was being handled *during* a timer callback.
My next step was to examine the locking primitives used within `kvm_xen_set_evtchn_fast`. I saw it attempting to acquire two locks: `gpc->lock` and `kvm->srcu`. My initial thought was about the interaction between these locks and potential race conditions.
Then, I specifically looked at the `srcu_read_lock(&kvm->srcu)` call. I questioned whether `srcu_read_lock` was a sleeping lock, especially in the context of PREEMPT_RT. My understanding is that `srcu_read_lock` is *not* a sleeping lock. This was a point of confusion for a moment, but it quickly became clear that the `srcu` lock itself wasn't the primary issue.
The stack trace was the key here. It showed the acquisition attempt for `&kvm->srcu` and, more importantly, for `&gpc->lock`. This confirmed that it was indeed `gpc->lock` that was the problematic element.
Now, I know `gpc->lock` is a `rwlock_t`. In a PREEMPT_RT kernel, `rwlock_t` is mapped to `rt_rw_lock`. This is a critical piece of information because `rt_rw_lock` *is* a sleeping lock. The bug then became glaringly obvious: `kvm_xen_set_evtchn_fast` was attempting to acquire a sleeping lock (`gpc->lock`) while running in a hardirq context. This is a fundamental violation of PREEMPT_RT rules and leads to deadlocks.
Looking at the user's provided C reproducer, I see it's already quite robust. It successfully sets up the VM, the VCPU, and the timer attribute. The feedback from the oracle confirms that the environment probe was successful and that `/dev/kvm` is accessible. This tells me the core setup of the reproducer is sound.
The prompt asks me to translate the diagnostic into concrete instructions for the repro-generator. Given that the candidate program is already functional in its basic setup, my next step is to instruct the generator to proceed with the existing code. I might also consider suggesting minor enhancements to ensure the timer actually fires and the race condition is reliably triggered, such as explicitly pinning the process to a CPU or ensuring the timer is configured to fire promptly.
I'm also double-checking if `kvm_xen_set_evtchn_fast` has any other prerequisites or checks that need to be explicitly addressed in the reproducer. For instance, does it validate the event channel itself before attempting to lock? This is something I would want to ensure is implicitly handled by the existing setup or explicitly added if necessary to guarantee the bug is hit.
|
| 90/5 |
2026/08/12 13:25 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c Name:kvm_xen_set_evtchn_fast]
Results: map[SourceCode:1792: /*
1793: * The return value from this function is propagated to kvm_set_irq() API,
1794: * so it returns:
1795: * < 0 Interrupt was ignored (masked or not delivered for other reasons)
1796: * = 0 Interrupt was coalesced (previous irq is still pending)
1797: * > 0 Number of CPUs interrupt was delivered to
1798: *
1799: * It is also called directly from kvm_arch_set_irq_inatomic(), where the
1800: * only check on its return value is a comparison with -EWOULDBLOCK'.
1801: */
1802: int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm)
1803: {
1804: struct gfn_to_pfn_cache *gpc = &kvm->arch.xen.shinfo_cache;
1805: struct kvm_vcpu *vcpu;
1806: unsigned long *pending_bits, *mask_bits;
1807: unsigned long flags;
1808: int port_word_bit;
1809: bool kick_vcpu = false;
1810: int vcpu_idx, idx, rc;
1811:
1812: vcpu_idx = READ_ONCE(xe->vcpu_idx);
1813: if (vcpu_idx >= 0)
1814: vcpu = kvm_get_vcpu(kvm, vcpu_idx);
1815: else {
1816: vcpu = kvm_get_vcpu_by_id(kvm, xe->vcpu_id);
1817: if (!vcpu)
1818: return -EINVAL;
1819: WRITE_ONCE(xe->vcpu_idx, vcpu->vcpu_idx);
1820: }
1821:
1822: if (xe->port >= max_evtchn_port(kvm))
1823: return -EINVAL;
1824:
1825: rc = -EWOULDBLOCK;
1826:
1827: idx = srcu_read_lock(&kvm->srcu);
1828:
1829: read_lock_irqsave(&gpc->lock, flags);
1830: if (!kvm_gpc_check(gpc, PAGE_SIZE))
1831: goto out_rcu;
1832:
1833: if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
1834: struct shared_info *shinfo = gpc->khva;
1835: pending_bits = (unsigned long *)&shinfo->evtchn_pending;
1836: mask_bits = (unsigned long *)&shinfo->evtchn_mask;
1837: port_word_bit = xe->port / 64;
1838: } else {
1839: struct compat_shared_info *shinfo = gpc->khva;
1840: pending_bits = (unsigned long *)&shinfo->evtchn_pending;
1841: mask_bits = (unsigned long *)&shinfo->evtchn_mask;
1842: port_word_bit = xe->port / 32;
1843: }
1844:
1845: /*
1846: * If this port wasn't already set, and if it isn't masked, then
1847: * we try to set the corresponding bit in the in-kernel shadow of
1848: * evtchn_pending_sel for the target vCPU. And if *that* wasn't
1849: * already set, then we kick the vCPU in question to write to the
1850: * *real* evtchn_pending_sel in its own guest vcpu_info struct.
1851: */
1852: if (test_and_set_bit(xe->port, pending_bits)) {
1853: rc = 0; /* It was already raised */
1854: } else if (test_bit(xe->port, mask_bits)) {
1855: rc = -ENOTCONN; /* Masked */
1856: kvm_xen_check_poller(vcpu, xe->port);
1857: } else {
1858: rc = 1; /* Delivered to the bitmap in shared_info. */
1859: /* Now switch to the vCPU's vcpu_info to set the index and pending_sel */
1860: read_unlock_irqrestore(&gpc->lock, flags);
1861: gpc = &vcpu->arch.xen.vcpu_info_cache;
1862:
1863: read_lock_irqsave(&gpc->lock, flags);
1864: if (!kvm_gpc_check(gpc, sizeof(struct vcpu_info))) {
1865: /*
1866: * Could not access the vcpu_info. Set the bit in-kernel
1867: * and prod the vCPU to deliver it for itself.
1868: */
1869: if (!test_and_set_bit(port_word_bit, &vcpu->arch.xen.evtchn_pending_sel))
1870: kick_vcpu = true;
1871: goto out_rcu;
1872: }
1873:
1874: if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
1875: struct vcpu_info *vcpu_info = gpc->khva;
1876: if (!test_and_set_bit(port_word_bit, &vcpu_info->evtchn_pending_sel)) {
1877: WRITE_ONCE(vcpu_info->evtchn_upcall_pending, 1);
1878: kick_vcpu = true;
1879: }
1880: } else {
1881: struct compat_vcpu_info *vcpu_info = gpc->khva;
1882: if (!test_and_set_bit(port_word_bit,
1883: (unsigned long *)&vcpu_info->evtchn_pending_sel)) {
1884: WRITE_ONCE(vcpu_info->evtchn_upcall_pending, 1);
1885: kick_vcpu = true;
1886: }
1887: }
1888:
1889: /* For the per-vCPU lapic vector, deliver it as MSI. */
1890: if (kick_vcpu && vcpu->arch.xen.upcall_vector) {
1891: kvm_xen_inject_vcpu_vector(vcpu);
1892: kick_vcpu = false;
1893: }
1894: }
1895:
1896: out_rcu:
1897: read_unlock_irqrestore(&gpc->lock, flags);
1898: srcu_read_unlock(&kvm->srcu, idx);
1899:
1900: if (kick_vcpu) {
1901: kvm_make_request(KVM_REQ_UNBLOCK, vcpu);
1902: kvm_vcpu_kick(vcpu);
1903: }
1904:
1905: return rc;
1906: }
SourceFile:arch/x86/kvm/xen.c]
|
| 91/5 |
2026/08/12 13:25 |
llm |
strategy-refiner |
0m
Model:
Tokens:
input: 19509
output: 44
thoughts: 147
Thoughts: **A Subtle Race Condition in KVM Xen Event Channel Handling**
My analysis has uncovered a potential race condition within the KVM Xen event channel handling mechanism, specifically concerning the `kvm_xen_set_evtchn_fast` function. My current understanding is that this function attempts to access `kvm->arch.xen.shinfo_cache`. A critical point of concern is what happens if `shinfo_cache` hasn't been properly initialized. In such a scenario, the subsequent call to `kvm_gpc_check(gpc, PAGE_SIZE)` would likely fail. This failure, based on the control flow, would lead to a jump to the `out_rcu` label.
However, my immediate thought process then grappled with a crucial observation: the code unconditionally executes `read_lock_irqsave(&gpc->lock, flags);` *before* `kvm_gpc_check` is even called. This is where the bug's pervasiveness becomes apparent. Because `gpc->lock` is initialized at VM creation, this lock acquisition will *always* occur, irrespective of whether `shinfo_cache` has been set up or not. Consequently, this means the problematic path, leading to the potential `kvm_gpc_check` failure and subsequent jump to `out_rcu`, can be triggered at any time, even if `shinfo_cache` is in a valid state. This unconditional lock acquisition before the check is what allows the bug to manifest, regardless of the `shinfo_cache`'s initialization status. I need to rigorously verify this logic.
|
| 92/5 |
2026/08/12 13:25 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c Name:kvm_xen_init_vm]
Results: map[SourceCode:2335: void kvm_xen_init_vm(struct kvm *kvm)
2336: {
2337: mutex_init(&kvm->arch.xen.xen_lock);
2338: idr_init(&kvm->arch.xen.evtchn_ports);
2339: kvm_gpc_init(&kvm->arch.xen.shinfo_cache, kvm);
2340: }
SourceFile:arch/x86/kvm/xen.c]
|
| 93/5 |
2026/08/12 13:25 |
llm |
strategy-refiner |
0m
Model:
Tokens:
input: 19831
output: 41
thoughts: 14
Thoughts: **My Thought Process**
Alright, so I'm looking at this code, specifically the `kvm_gpc_init` function. My immediate takeaway, based on what I'm seeing, is that its primary role here is to get the `kvm_gpc` subsystem up and running, and a critical part of that initialization is setting up a lock. This tells me that the `kvm_gpc` components are going to be dealing with concurrency – there will likely be multiple threads or processes accessing shared resources within this subsystem. Therefore, ensuring proper synchronization is paramount, and this function is where that crucial locking mechanism is being established.
|
| 94/5 |
2026/08/12 13:25 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:virt/kvm/pfncache.c Name:kvm_gpc_init]
Results: map[SourceCode: 385: void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm)
386: {
387: rwlock_init(&gpc->lock);
388: mutex_init(&gpc->refresh_lock);
389:
390: gpc->kvm = kvm;
391: gpc->pfn = KVM_PFN_ERR_FAULT;
392: gpc->gpa = INVALID_GPA;
393: gpc->uhva = KVM_HVA_ERR_BAD;
394: gpc->active = gpc->valid = false;
395: }
SourceFile:virt/kvm/pfncache.c]
|
| 95/5 |
2026/08/12 13:25 |
llm |
strategy-refiner |
0m
Model:
Tokens:
input: 20092
output: 44
thoughts: 217
Thoughts: **The Core of the Issue: Uninitialized Lock and Timer Interaction**
Alright, so I've been digging into this KVM/Xen timer situation, and it seems I've nailed down the crux of the problem. My initial thought was confirmed: `rwlock_init(&gpc->lock)` *is* indeed called during VM initialization. This is crucial because it means the lock is properly set up before the critical operations begin.
The real kicker, though, is how this ties into the timer. I've realized that the bug will trigger simply by calling `kvm_xen_set_evtchn_fast`. And the path to that function is quite direct: it's called by `xen_timer_callback`, which in turn is triggered by the hrtimer. So, the sequence is: hrtimer fires -> `xen_timer_callback` is invoked -> `kvm_xen_set_evtchn_fast` is called, and *there's* the potential race condition.
Based on this, I'm confident that the C reproducer I provided earlier should be perfectly sufficient to demonstrate the bug. It directly targets this problematic call path.
Now, to be absolutely sure, I wanted to double-check that the timer is actually firing as expected. I've looked at the provided code snippet for arming the timer:
```c
attr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
attr.u.timer.port = 1;
attr.u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
attr.u.timer.expires_ns = 1000000000ULL; /* 1 second */
```
The timer is being armed with `expires_ns`, which means it's set to expire after one second. This confirms the timer *is* configured to go off. My next step was to then examine `kvm_xen_start_timer` to see how it handles the armed timer and its associated operations, which is where I suspect the race condition is ultimately exposed.
|
| 96/5 |
2026/08/12 13:25 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c Name:kvm_xen_start_timer]
Results: map[SourceCode: 187: static void kvm_xen_start_timer(struct kvm_vcpu *vcpu, u64 guest_abs,
188: bool linux_wa)
189: {
190: struct kvm_vcpu_xen *xen = &vcpu->arch.xen;
191: int64_t kernel_now, delta;
192: uint64_t guest_now;
193: int r = -EOPNOTSUPP;
194:
195: /*
196: * The guest provides the requested timeout in absolute nanoseconds
197: * of the KVM clock — as *it* sees it, based on the scaled TSC and
198: * the pvclock information provided by KVM.
199: *
200: * The kernel doesn't support hrtimers based on CLOCK_MONOTONIC_RAW
201: * so use CLOCK_MONOTONIC. In the timescales covered by timers, the
202: * difference won't matter much as there is no cumulative effect.
203: *
204: * Calculate the time for some arbitrary point in time around "now"
205: * in terms of both kvmclock and CLOCK_MONOTONIC. Calculate the
206: * delta between the kvmclock "now" value and the guest's requested
207: * timeout, apply the "Linux workaround" described below, and add
208: * the resulting delta to the CLOCK_MONOTONIC "now" value, to get
209: * the absolute CLOCK_MONOTONIC time at which the timer should
210: * fire.
211: */
212: do {
213: struct pvclock_vcpu_time_info hv_clock;
214: uint64_t host_tsc, guest_tsc;
215:
216: if (!cpu_feature_enabled(X86_FEATURE_CONSTANT_TSC) ||
217: !vcpu->kvm->arch.use_master_clock)
218: break;
219:
220: /*
221: * If both Xen PV clocks are active, arbitrarily try to use the
222: * compat clock first, but also try to use the non-compat clock
223: * if the compat clock is unusable. The two PV clocks hold the
224: * same information, but it's possible one (or both) is stale
225: * and/or currently unreachable.
226: */
227: if (xen->vcpu_info_cache.active)
228: r = xen_get_guest_pvclock(vcpu, &hv_clock, &xen->vcpu_info_cache,
229: offsetof(struct compat_vcpu_info, time));
230: if (r && xen->vcpu_time_info_cache.active)
231: r = xen_get_guest_pvclock(vcpu, &hv_clock, &xen->vcpu_time_info_cache, 0);
232: if (r)
233: break;
234:
235: if (!IS_ENABLED(CONFIG_64BIT) ||
236: !kvm_get_monotonic_and_clockread(&kernel_now, &host_tsc)) {
237: /*
238: * Don't fall back to get_kvmclock_ns() because it's
239: * broken; it has a systemic error in its results
240: * because it scales directly from host TSC to
241: * nanoseconds, and doesn't scale first to guest TSC
242: * and *then* to nanoseconds as the guest does.
243: *
244: * There is a small error introduced here because time
245: * continues to elapse between the ktime_get() and the
246: * subsequent rdtsc(). But not the systemic drift due
247: * to get_kvmclock_ns().
248: */
249: kernel_now = ktime_get(); /* This is CLOCK_MONOTONIC */
250: host_tsc = rdtsc();
251: }
252:
253: /* Calculate the guest kvmclock as the guest would do it. */
254: guest_tsc = kvm_read_l1_tsc(vcpu, host_tsc);
255: guest_now = __pvclock_read_cycles(&hv_clock, guest_tsc);
256: } while (0);
257:
258: if (r) {
259: /*
260: * Without CONSTANT_TSC, get_kvmclock_ns() is the only option.
261: *
262: * Also if the guest PV clock hasn't been set up yet, as is
263: * likely to be the case during migration when the vCPU has
264: * not been run yet. It would be possible to calculate the
265: * scaling factors properly in that case but there's not much
266: * point in doing so. The get_kvmclock_ns() drift accumulates
267: * over time, so it's OK to use it at startup. Besides, on
268: * migration there's going to be a little bit of skew in the
269: * precise moment at which timers fire anyway. Often they'll
270: * be in the "past" by the time the VM is running again after
271: * migration.
272: */
273: guest_now = get_kvmclock_ns(vcpu->kvm);
274: kernel_now = ktime_get();
275: }
276:
277: delta = guest_abs - guest_now;
278:
279: /*
280: * Xen has a 'Linux workaround' in do_set_timer_op() which checks for
281: * negative absolute timeout values (caused by integer overflow), and
282: * for values about 13 days in the future (2^50ns) which would be
283: * caused by jiffies overflow. For those cases, Xen sets the timeout
284: * 100ms in the future (not *too* soon, since if a guest really did
285: * set a long timeout on purpose we don't want to keep churning CPU
286: * time by waking it up). Emulate Xen's workaround when starting the
287: * timer in response to __HYPERVISOR_set_timer_op.
288: */
289: if (linux_wa &&
290: unlikely((int64_t)guest_abs < 0 ||
291: (delta > 0 && (uint32_t) (delta >> 50) != 0))) {
292: delta = 100 * NSEC_PER_MSEC;
293: guest_abs = guest_now + delta;
294: }
295:
296: /*
297: * Avoid races with the old timer firing. Checking timer_expires
298: * to avoid calling hrtimer_cancel() will only have false positives
299: * so is fine.
300: */
301: if (vcpu->arch.xen.timer_expires)
302: hrtimer_cancel(&vcpu->arch.xen.timer);
303:
304: atomic_set(&vcpu->arch.xen.timer_pending, 0);
305: vcpu->arch.xen.timer_expires = guest_abs;
306:
307: if (delta <= 0)
308: xen_timer_callback(&vcpu->arch.xen.timer);
309: else
310: hrtimer_start(&vcpu->arch.xen.timer,
311: ktime_add_ns(kernel_now, delta),
312: HRTIMER_MODE_ABS_HARD);
313: }
SourceFile:arch/x86/kvm/xen.c]
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| 97/5 |
2026/08/12 13:25 |
llm |
strategy-refiner |
0m
Model:
Tokens:
input: 22608
output: 45
thoughts: 354
Thoughts: **My Thought Process Regarding the KVM Xen Timer Bug**
My initial hypothesis about the `kvm_xen_start_timer` function was that a `delta <= 0` condition would lead to a synchronous call of `xen_timer_callback`. I reasoned that this synchronous execution, occurring within the context of an ioctl (a task context), would *not* trigger the observed bug, as the bug was reported in a hardirq context. Therefore, my immediate deduction was that for the bug to manifest, `delta` *must* be greater than zero.
I then delved into the calculation of `delta`: `guest_abs - guest_now;`. I identified `guest_abs` as `data->u.timer.expires_ns` and `guest_now` as `get_kvmclock_ns(vcpu->kvm)`. My understanding was that since the PV clock isn't yet set up, `get_kvmclock_ns` defaults to returning the current KVM clock time. Crucially, I recalled that when a VM is initially created, the KVM clock starts at or very near zero.
This led me to a specific scenario: if I were to set `expires_ns` to a value like 1,000,000,000 nanoseconds (1 second), `guest_now` would be a small value. Consequently, `delta` would approximate 1 second, satisfying the `delta > 0` condition. This would then lead to `hrtimer_start` being invoked with `HRTIMER_MODE_ABS_HARD`. My conclusion was that the timer would indeed fire in a hardirq context after that 1-second delay, perfectly aligning with the bug report.
However, a nagging doubt surfaced. I began to question if there was any possibility that `guest_now` could be *larger* than the 1-second `expires_ns` value I was considering. I recalled that `get_kvmclock_ns` relies on `ktime_get_boottime_ns()` with some offset. This prompted me to revisit the exact implementation of `get_kvmclock_ns` to confirm this potential edge case.
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2026/08/12 13:25 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/x86.c Name:get_kvmclock_ns]
Results: map[SourceCode:1707: u64 get_kvmclock_ns(struct kvm *kvm)
1708: {
1709: struct kvm_clock_data data;
1710:
1711: get_kvmclock(kvm, &data);
1712: return data.clock;
1713: }
SourceFile:arch/x86/kvm/x86.c]
|
| 99/5 |
2026/08/12 13:25 |
llm |
strategy-refiner |
0m
Model:
Tokens:
input: 23119
output: 43
thoughts: 8
Thoughts: **My Thought Process**
Okay, so I'm looking at this line, and it's simply `get_kvmclock`. This immediately tells me a few things, and my internal "expert mode" kicks in.
First, the name itself, `get_kvmclock`. The `get_` prefix strongly suggests this is a function call, and its purpose is to retrieve some kind of information. The core of the name is `kvmclock`. This points directly to something related to KVM (Kernel-based Virtual Machine) and its clock mechanism.
So, my initial hypothesis is: this line is invoking a function that retrieves the current state or value of the KVM clock.
Now, as an expert, I'm not just thinking about *what* it does, but *why* it might be doing it and in what context.
* **What is the KVM clock?** I know the KVM clock is a virtualized representation of time for a guest VM. It's crucial for maintaining time synchronization within the guest, for scheduling guest operations, and for providing a consistent time source even when the host's time might fluctuate or be unavailable.
* **Why would I need to `get_kvmclock`?**
* **Time Synchronization:** The most obvious reason. If I'm implementing a time synchronization mechanism within the guest, or if I'm a hypervisor management tool needing to read the guest's perception of time, I'd need to fetch this value.
* **Guest State Analysis:** Understanding the guest's internal clock can be vital for debugging or performance analysis. For instance, if a guest is experiencing significant clock drift, this call might be part of a diagnostic routine.
* **Event Timestamps:** In systems where events are logged or processed, using the KVM clock for timestamps ensures that events are ordered and analyzed within the VM's temporal context, independent of the host's potentially differing clock.
* **Scheduling/Tick Management:** The KVM clock is intimately tied to how the hypervisor schedules and delivers virtual ticks to the guest. This function could be used to query the current tick count or related temporal information.
* **What are the potential implications?**
* **Performance Overhead:** Accessing KVM-specific hardware or virtualized structures can incur some overhead. I'd be mindful of how frequently this function is called and if it's a performance bottleneck.
* **Context Dependency:** The value returned by `get_kvmclock` will be specific to the context of the running KVM guest. It's not a global system clock in the same way a host's real-time clock is.
* **Underlying Implementation:** While the function name is generic, the underlying implementation could be complex. It might involve reading from specific MSRs (Model-Specific Registers), interacting with a virtual hardware device, or querying internal hypervisor state. As an expert, I'd anticipate needing to understand this if I were digging deeper.
* **Error Handling:** What happens if the KVM clock isn't available or accessible? The function would likely have error return codes or exceptions to consider.
In essence, seeing `get_kvmclock` is a clear signal that I'm dealing with virtualized time within a KVM environment. My next step, if this were code I was actively analyzing, would be to look at where this function is defined and how its return value is being used to understand the specific intent in this particular piece of code. But the core meaning is unequivocally about retrieving KVM guest clock information.
|
| 100/5 |
2026/08/12 13:25 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/x86.c Name:get_kvmclock]
Results: map[SourceCode:1696: static void get_kvmclock(struct kvm *kvm, struct kvm_clock_data *data)
1697: {
1698: struct kvm_arch *ka = &kvm->arch;
1699: unsigned seq;
1700:
1701: do {
1702: seq = read_seqcount_begin(&ka->pvclock_sc);
1703: __get_kvmclock(kvm, data);
1704: } while (read_seqcount_retry(&ka->pvclock_sc, seq));
1705: }
SourceFile:arch/x86/kvm/x86.c]
|
| 101/5 |
2026/08/12 13:25 |
llm |
strategy-refiner |
0m
Model:
Tokens:
input: 23350
output: 44
thoughts: 9
Thoughts: **My Inner Monologue on KVM Clock Initialization**
Alright, let's dive into what's happening here. So, I'm currently processing the flow, and the next logical step, or rather, the thing I'm explicitly seeing and thinking about, is the `__get_kvmclock` function. It's not just a random piece of code; it signifies a crucial point in the initialization process, specifically where I need to acquire or understand information related to the KVM (Kernel-based Virtual Machine) clock. This implies that I'm either about to set up a virtualized environment, or I'm operating within one, and need to synchronize or access the host's timing mechanisms. This function name suggests a retrieval operation – I need to *get* the KVM clock. This is foundational for any time-sensitive operations within the guest or for the hypervisor's management of time for the VM. It’s about establishing a reliable time source, which is paramount for scheduling, logging, and all sorts of operational integrity within the virtualized context.
|
| 102/5 |
2026/08/12 13:25 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/x86.c Name:__get_kvmclock]
Results: map[SourceCode:1660: /* Called within read_seqcount_begin/retry for kvm->pvclock_sc. */
1661: static void __get_kvmclock(struct kvm *kvm, struct kvm_clock_data *data)
1662: {
1663: struct kvm_arch *ka = &kvm->arch;
1664: struct pvclock_vcpu_time_info hv_clock;
1665:
1666: /* both __this_cpu_read() and rdtsc() should be on the same cpu */
1667: get_cpu();
1668:
1669: data->flags = 0;
1670: if (ka->use_master_clock &&
1671: (cpu_feature_enabled(X86_FEATURE_CONSTANT_TSC) || __this_cpu_read(cpu_tsc_khz))) {
1672: #ifdef CONFIG_X86_64
1673: struct timespec64 ts;
1674:
1675: if (kvm_get_walltime_and_clockread(&ts, &data->host_tsc)) {
1676: data->realtime = ts.tv_nsec + NSEC_PER_SEC * ts.tv_sec;
1677: data->flags |= KVM_CLOCK_REALTIME | KVM_CLOCK_HOST_TSC;
1678: } else
1679: #endif
1680: data->host_tsc = rdtsc();
1681:
1682: data->flags |= KVM_CLOCK_TSC_STABLE;
1683: hv_clock.tsc_timestamp = ka->master_cycle_now;
1684: hv_clock.system_time = ka->master_kernel_ns + ka->kvmclock_offset;
1685: kvm_get_time_scale(NSEC_PER_SEC, get_cpu_tsc_khz() * 1000LL,
1686: &hv_clock.tsc_shift,
1687: &hv_clock.tsc_to_system_mul);
1688: data->clock = __pvclock_read_cycles(&hv_clock, data->host_tsc);
1689: } else {
1690: data->clock = get_kvmclock_base_ns() + ka->kvmclock_offset;
1691: }
1692:
1693: put_cpu();
1694: }
SourceFile:arch/x86/kvm/x86.c]
|
| 103/5 |
2026/08/12 13:25 |
llm |
strategy-refiner |
0m
Model:
Tokens:
input: 24084
output: 45
thoughts: 1269
Thoughts: **My Thought Process on KVM Xen Timer Reproducer Generation**
Here's a breakdown of my reasoning process as I worked through generating the KVM Xen timer reproducer:
Initially, my understanding of the KVM clock mechanism was that `get_kvmclock_base_ns()` provides the boot time, and `ka->kvmclock_offset` is initialized by subtracting this value. This leads to `data->clock` starting at zero upon VM creation, meaning `guest_now` effectively tracks time elapsed since the VM's inception.
My first thought was that setting an expiration time, `expires_ns`, to, say, 1 second, would be perfectly safe. If the system is running fast, the time difference, `delta`, would be just under 1 second when the timer is checked, which seemed robust.
However, a critical doubt immediately arose: what happens if the `sleep(2)` call is interrupted, or if the process terminates *before* the timer event actually fires? I recognized that if the process exits, the VM is destroyed, and crucially, any associated timers would be canceled. This meant my initial assumption of `sleep(2)` being sufficient was flawed. I needed to guarantee the process *waits* for the timer to fire.
My next step was to investigate the VM and timer destruction sequence. I questioned if `kvm_destroy_vm` would cancel the timer. Then, I realized that timers are typically per-VCPU. This led me to check `kvm_arch_vcpu_destroy` and confirm that, indeed, the VCPU destruction is what cancels the timer. Therefore, I *must* ensure the timer fires before the VCPU (and thus the process) is allowed to exit. While `sleep(2)` is a common practice, to be absolutely certain, I considered alternatives like a loop or `pause()`, but ultimately concluded that `sleep(2)` should be sufficient for a reproducer, given the context of a controlled test environment.
Moving on to the repro-generator instructions, I noted the oracle feedback: "The environment probe was successful. `/dev/kvm` is accessible. Please proceed to generate the full reproducer in the next iteration." This clearly indicated that the core task was simply to output the C reproducer code.
Then, a slight confusion arose from the prompt's phrasing: "Analyze the technical diagnosis provided in the oracle feedback and translate it into concrete, step-by-step instructions for the repro-generator on how to modify the code structure, alignments, offsets, or parameters of the candidate program." My initial candidate program, based on my understanding, was already correct. So, instead of modifying anything, my interpretation became that I needed to instruct the repro-generator to simply *use* the correct C code I had devised. My focus then shifted to ensuring the C code itself was as robust and complete as possible.
This led to refining the C code. I reviewed the necessary includes (`fcntl.h`, `sys/ioctl.h`, `linux/kvm.h`, `stdint.h`, `unistd.h`, `stdio.h`). I also looked up and defined necessary constants like `KVM_XEN_VCPU_ATTR_TYPE_TIMER` and `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL` as they might not be universally present in all kernel headers. I then constructed the `my_kvm_xen_vcpu_attr` struct, paying close attention to its union and the specific `timer` member. I also defined the `MY_KVM_XEN_VCPU_SET_ATTR` ioctl macro.
The `main` function was straightforward: opening `/dev/kvm`, creating a VM, creating a VCPU, and then populating the `attr` struct with the timer configuration (`type`, `port`, `priority`, and `expires_ns` set to 1 second). Finally, I applied this attribute using `ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr)` and then executed `sleep(2)` to wait for the timer to expire.
A final self-reflection occurred: I pondered if any other KVM Xen setup was required *before* setting VCPU attributes, specifically questioning if `KVM_XEN_HVM_CONFIG` needed to be called on the VM. This is a crucial consideration for ensuring the environment is correctly prepared for Xen-specific VCPU operations.
|
| 104/5 |
2026/08/12 13:25 |
tool |
codesearch-definition-source |
0m
Args: map[ContextFile:arch/x86/kvm/xen.c Name:kvm_xen_hvm_config]
Results: map[SourceCode:1365: int kvm_xen_hvm_config(struct kvm *kvm, struct kvm_xen_hvm_config *xhc)
1366: {
1367: /* Only some feature flags need to be *enabled* by userspace */
1368: u32 permitted_flags = KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL |
1369: KVM_XEN_HVM_CONFIG_EVTCHN_SEND |
1370: KVM_XEN_HVM_CONFIG_PVCLOCK_TSC_UNSTABLE;
1371: u32 old_flags;
1372:
1373: if (xhc->flags & ~permitted_flags)
1374: return -EINVAL;
1375:
1376: /*
1377: * With hypercall interception the kernel generates its own
1378: * hypercall page so it must not be provided.
1379: */
1380: if ((xhc->flags & KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL) &&
1381: (xhc->blob_addr_32 || xhc->blob_addr_64 ||
1382: xhc->blob_size_32 || xhc->blob_size_64))
1383: return -EINVAL;
1384:
1385: /*
1386: * Restrict the MSR to the range that is unofficially reserved for
1387: * synthetic, virtualization-defined MSRs, e.g. to prevent confusing
1388: * KVM by colliding with a real MSR that requires special handling.
1389: */
1390: if (xhc->msr &&
1391: (xhc->msr < KVM_XEN_MSR_MIN_INDEX || xhc->msr > KVM_XEN_MSR_MAX_INDEX))
1392: return -EINVAL;
1393:
1394: mutex_lock(&kvm->arch.xen.xen_lock);
1395:
1396: if (xhc->msr && !kvm->arch.xen.hvm_config.msr)
1397: static_branch_inc(&kvm_xen_enabled.key);
1398: else if (!xhc->msr && kvm->arch.xen.hvm_config.msr)
1399: static_branch_slow_dec_deferred(&kvm_xen_enabled);
1400:
1401: old_flags = kvm->arch.xen.hvm_config.flags;
1402: memcpy(&kvm->arch.xen.hvm_config, xhc, sizeof(*xhc));
1403:
1404: mutex_unlock(&kvm->arch.xen.xen_lock);
1405:
1406: if ((old_flags ^ xhc->flags) & KVM_XEN_HVM_CONFIG_PVCLOCK_TSC_UNSTABLE)
1407: kvm_make_all_cpus_request(kvm, KVM_REQ_CLOCK_UPDATE);
1408:
1409: return 0;
1410: }
SourceFile:arch/x86/kvm/xen.c]
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| 105/5 |
2026/08/12 13:25 |
llm |
strategy-refiner |
0m
Model:
Tokens:
input: 26278
output: 965
thoughts: 765
Thoughts: **My Thought Process on Exploiting the KVM Xen Timer Bug**
Okay, so my initial thought was whether `kvm_xen_hvm_config` was absolutely essential for `kvm_xen_vcpu_set_attr` to function. I suspected it wasn't because `kvm_xen_vcpu_set_attr` itself doesn't seem to check for a global Xen enablement flag. I decided to double-check that assumption by looking more closely at `kvm_xen_vcpu_set_attr`. My investigation confirmed that the function primarily focuses on acquiring the `xen_lock` and then processing the provided attribute. This means a standalone C program manipulating the attribute directly should be sufficient.
Now, for the specifics of the `KVM_XEN_VCPU_ATTR_TYPE_TIMER` attribute, I recalled a few critical requirements. First, the `data->u.timer.port` needs to be non-zero. In my planned C code, I've set this to `1`. Second, the `data->u.timer.priority` must be set to `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL`. My code also reflects this. Finally, and crucially for triggering the timer, `data->u.timer.expires_ns` must be non-zero. I've chosen to set this to `1000000000ULL`, which translates to one second from now, ensuring the timer will indeed fire.
With these details ironed out, I feel confident that the approach is robust and will accurately reproduce the bug. I'm now ready to formulate the exact instructions for the repro-generator to ensure it captures all the necessary steps.
Here's how I'll instruct the repro-generator:
1. **Include Necessary Headers:** I need `<fcntl.h>` for file control, `<sys/ioctl.h>` for the ioctl system call, `<linux/kvm.h>` for KVM definitions, `<stdint.h>` for integer types, `<unistd.h>` for standard Unix functions like `sleep`, and `<stdio.h>` for input/output.
2. **Define Constants (if not present):** It's important to define `KVM_XEN_VCPU_ATTR_TYPE_TIMER` as `0x7` and `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL` as `((uint32_t)(-1))` in case these specific definitions aren't readily available in the user's environment, to avoid header compatibility issues.
3. **Local Struct Definition:** To further mitigate potential header mismatches, I'll define the `my_kvm_xen_vcpu_attr` struct locally within the C code.
4. **Define Custom IOCTL:** I'll define `MY_KVM_XEN_VCPU_SET_ATTR` as `_IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)`. This ensures we're using the correct ioctl number for setting the Xen VCPU attribute.
5. **Main Program Logic:**
* Open `/dev/kvm` to interact with the KVM module.
* Create a virtual machine using the `KVM_CREATE_VM` ioctl.
* Create a virtual CPU (VCPU) using the `KVM_CREATE_VCPU` ioctl.
* Initialize the `my_kvm_xen_vcpu_attr` struct with the specific values I've determined:
* `type = KVM_XEN_VCPU_ATTR_TYPE_TIMER`
* `u.timer.port = 1`
* `u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL`
* `u.timer.expires_ns = 1000000000ULL` (one second in the future).
* Execute the `MY_KVM_XEN_VCPU_SET_ATTR` ioctl on the VCPU file descriptor, passing the prepared attribute structure.
* Crucially, I'll include a `sleep(2)` call. This delay is essential to allow the high-resolution timer (hrtimer) to expire in its hardirq context, which is the specific timing that triggers the bug I'm aiming to reproduce.
I'm confident that this set of instructions will produce a reliable reproduction of the issue for the user, given their expertise.
|
| 106/3 |
2026/08/12 13:26 |
action |
merge-strategy |
0m
Results: map[CurrentReproStrategy:The environment probe confirms that `/dev/kvm` is accessible and the basic KVM setup works. We can now proceed to generate the full C reproducer.
### Bug Analysis
The bug is a "sleeping function called from invalid context" in `kvm_xen_set_evtchn_fast()`, which occurs on `PREEMPT_RT` kernels.
1. The Xen timer is armed via the `KVM_XEN_VCPU_SET_ATTR` ioctl.
2. If the timer's expiration time is in the future, KVM arms an asynchronous hrtimer (`HRTIMER_MODE_ABS_HARD`).
3. When the timer expires, `xen_timer_callback()` executes in **hardirq context**.
4. The callback invokes `kvm_xen_set_evtchn_fast()`, which attempts to acquire `gpc->lock` (a `rwlock_t`).
5. On `PREEMPT_RT`, `rwlock_t` is mapped to a sleeping lock (`rt_rw_lock`). Acquiring a sleeping lock in hardirq context is invalid and triggers the BUG.
### Reproduction Strategy
To trigger the bug, we just need to arm the Xen timer with an expiration time safely in the future (e.g., 1 second) so that it fires asynchronously in hardirq context.
Please generate the C reproducer using the following step-by-step instructions:
1. **Include Headers**: Include `<fcntl.h>`, `<sys/ioctl.h>`, `<linux/kvm.h>`, `<stdint.h>`, `<unistd.h>`, and `<stdio.h>`.
2. **Define Constants**: Define `KVM_XEN_VCPU_ATTR_TYPE_TIMER` as `0x7` and `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL` as `((uint32_t)(-1))` to ensure compatibility with older headers.
3. **Define Attribute Struct**: Define a local version of the Xen VCPU attribute struct to avoid missing definitions in older kernel headers:
```c
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
#define MY_KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
```
4. **KVM Setup**: In `main()`, open `/dev/kvm`, create a VM (`KVM_CREATE_VM`), and create a VCPU (`KVM_CREATE_VCPU`).
5. **Arm the Timer**:
- Initialize the `my_kvm_xen_vcpu_attr` struct to zero.
- Set `type` to `KVM_XEN_VCPU_ATTR_TYPE_TIMER`.
- Set `u.timer.port` to `1`.
- Set `u.timer.priority` to `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL`.
- Set `u.timer.expires_ns` to `1000000000ULL` (1 second).
- Call `ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr)`.
6. **Wait for Execution**: Add `sleep(2);` at the end of `main()` to keep the process alive long enough for the hrtimer to fire in the background and trigger the bug.]
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| 107/3 |
2026/08/12 13:26 |
agent |
repro-generator |
0m
Model:
Results: map[IsProbe:false RawCandidateReproC:#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
#define KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL ((uint32_t)(-1))
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
#define MY_KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
int main(void)
{
int kvm_fd, vm_fd, vcpu_fd;
struct my_kvm_xen_vcpu_attr attr;
int res;
kvm_fd = open("/dev/kvm", O_RDWR);
if (kvm_fd < 0) {
printf("[-] Failed to open /dev/kvm: %s\n", strerror(errno));
exit(1);
}
printf("[+] open /dev/kvm successful.\n");
vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0);
if (vm_fd < 0) {
printf("[-] Failed to KVM_CREATE_VM: %s\n", strerror(errno));
exit(1);
}
printf("[+] KVM_CREATE_VM successful.\n");
vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);
if (vcpu_fd < 0) {
printf("[-] Failed to KVM_CREATE_VCPU: %s\n", strerror(errno));
exit(1);
}
printf("[+] KVM_CREATE_VCPU successful.\n");
memset(&attr, 0, sizeof(attr));
attr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
attr.u.timer.port = 1;
attr.u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
attr.u.timer.expires_ns = 1000000000ULL;
res = ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr);
if (res < 0) {
printf("[-] Failed to MY_KVM_XEN_VCPU_SET_ATTR: %s\n", strerror(errno));
exit(1);
}
printf("[+] MY_KVM_XEN_VCPU_SET_ATTR successful.\n");
printf("[+] Waiting for timer to fire...\n");
sleep(2);
close(vcpu_fd);
close(vm_fd);
close(kvm_fd);
printf("[+] Done.\n");
return 0;
}
]
Instruction: You are a security researcher with deep Linux kernel background.
Your goal is to generate a minimal, standalone C program for the strictly defensive
purpose of verifying a bugfix in an isolated environment.
To ensure that we can diagnose why a program might fail to run on the test environment,
you MUST include detailed logging and error checking in the generated C program:
1. Use 'printf(...)' for all progress messages and error logs.
2. Every system call (e.g., socket, bind, listen, connect, ioctl, send) must check for a failure return value.
3. If a call fails, it must print a specific error message including the function name
and the error string (use strerror(errno)), and then exit with a non-zero status.
4. The program must print a message after every successful major step.
5. Generate code that follows this pattern for all operations:
int res = do_something();
if (res < 0) {
printf("[-] Failed to do_something: %s\n", strerror(errno));
exit(1);
}
printf("[+] do_something successful.\n");
6. The compilation and development environment (including compilers, build
systems, makefiles, and kernel build/header directories) is NOT available
on the target test VM guest. Do NOT check for, build, or reference any
compilation tools, build files, or kernel development directories.
7. Do NOT execute shell commands or run external binaries (e.g. by using
functions like 'system()', 'popen()', or the 'exec' family such as
'execve()'). All environment checks, capability probings, and reproduction
steps must be performed directly using standard Linux system calls (such
as 'open', 'socket', 'ioctl', 'stat', etc.).
8. When reproducing asynchronous kernel timeouts or warnings, always
include a sufficient delay (using sleep or similar) after deleting
or unregistering the device to allow the kernel's asynchronous
timeout to trigger before program exit.
=== PHASE 2: BUG REPRODUCTION (GENERATION) ===
You must now generate a full reproducer candidate attempting to trigger the target bug/crash.
Do NOT generate a probe program. Focus directly on triggering the bug/crash described in the description.
You can assume that all necessary kernel capabilities and privileges (e.g., access to /dev/vhci,
ability to load BPF programs, etc.) have already been verified and are available in the environment.
Do not spend too much time analyzing or trying to generate a perfect one-shot reproducer.
Instead, follow an iterative approach: generate a simple candidate, execute it, analyze the results,
and improve it. Keep your reasoning steps short and focused on the next logical experiment.
Prefer calling several tools at the same time to save round-trips.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt: Bug Description: BUG: sleeping function called from invalid context in kvm_xen_set_evtchn_fast
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:248
in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 5622, name: syz-executor363
preempt_count: 10000, expected: 0
RCU nest depth: 1, expected: 1
locks held by syz-executor363/5622: 4, last CPU#0:
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: __simple_recursive_removal+0x19a/0x520 fs/libfs.c:619
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
#2: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rtlock_slowlock_locked+0x2ab/0x3c20 kernel/locking/rtmutex.c:1874
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1be/0x990 arch/x86/kvm/xen.c:1827
irq event stamp: 13272
hardirqs last enabled at (13271): [<ffffffff8b53b4b3>] __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:187 [inline]
hardirqs last enabled at (13271): [<ffffffff8b53b4b3>] _raw_spin_unlock_irq+0x23/0x50 kernel/locking/spinlock.c:206
hardirqs last disabled at (13272): [<ffffffff8b501aee>] sysvec_apic_timer_interrupt+0xe/0xc0 arch/x86/kernel/apic/apic.c:1062
softirqs last enabled at (6940): [<ffffffff81882fe0>] __local_bh_enable_ip+0x1a0/0x2b0 kernel/softirq.c:305
softirqs last disabled at (6932): [<ffffffff891cda09>] local_bh_disable include/linux/bottom_half.h:20 [inline]
softirqs last disabled at (6932): [<ffffffff891cda09>] __alloc_skb+0x189/0x7a0 net/core/skbuff.c:697
Preemption disabled at:
[<ffffffff81883b8e>] irq_enter_rcu+0x1e/0x1f0 kernel/softirq.c:668
CPU: 0 UID: 0 PID: 5622 Comm: syz-executor363 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
__might_resched+0x329/0x480 kernel/sched/core.c:9194
rt_read_lock+0xa9/0x4b0 kernel/locking/spinlock_rt.c:248
kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x3a0/0xaf0 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x44a/0x900 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:rt_mutex_owner include/linux/rtmutex.h:52 [inline]
RIP: 0010:rtmutex_spin_on_owner kernel/locking/rtmutex.c:1504 [inline]
RIP: 0010:rtlock_slowlock_locked+0x34e5/0x3c20 kernel/locking/rtmutex.c:1893
Code: 80 3c 01 00 4c 8b b4 24 80 00 00 00 4c 8b 2c 24 74 08 4c 89 ef e8 db 0e df f6 48 8d 84 24 60 01 00 00 49 39 45 00 75 6c f3 90 <48> b8 00 00 00 00 00 fc ff df 48 8b 8c 24 a8 00 00 00 80 3c 01 00
RSP: 0018:ffffc90004e6f7a0 EFLAGS: 00000246
RAX: ffffc90004e6f900 RBX: 1ffff11006ff9bbe RCX: 1ffffffff1ca7871
RDX: 00000000e6b90d15 RSI: ffffffff8bcbd060 RDI: 0000000000000001
RBP: ffffc90004e6f9f0 R08: 1d00000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8e3c3880 R12: ffff888037fcddc0
R13: ffffffff8e53c388 R14: ffffffff8e53c390 R15: 1ffff11006ff9bba
rtlock_slowlock kernel/locking/rtmutex.c:1922 [inline]
rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
__rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
rt_spin_lock+0x165/0x400 kernel/locking/spinlock_rt.c:57
spin_lock include/linux/spinlock_rt.h:45 [inline]
simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
__simple_recursive_removal+0x215/0x520 fs/libfs.c:623
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:781
kvm_destroy_vm_debugfs virt/kvm/kvm_main.c:988 [inline]
kvm_destroy_vm virt/kvm/kvm_main.c:1261 [inline]
kvm_put_kvm+0x147/0xae0 virt/kvm/kvm_main.c:1331
kvm_vm_release+0x46/0x50 virt/kvm/kvm_main.c:1354
__fput+0x42a/0xa80 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x73a/0x2360 kernel/exit.c:1009
do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
__do_sys_exit_group kernel/exit.c:1163 [inline]
__se_sys_exit_group kernel/exit.c:1161 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1161
x64_sys_call+0x18bf/0x18c0 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f132ec60d05
Code: Unable to access opcode bytes at 0x7f132ec60cdb.
RSP: 002b:00007ffe413e3968 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f132ec60d05
RDX: 00000000000000e7 RSI: ffffffffffffffd8 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000009 R11: 0000000000000202 R12: 0000000000000000
R13: 00007f132ecfa118 R14: 00007f132ecfc3c8 R15: 00007f132ecfc3e0
</TASK>
=============================
[ BUG: Invalid wait context ]
syzkaller #0 Tainted: G W
-----------------------------
syz-executor363/5622 is trying to lock:
ffff888038241530 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
other info that might help us debug this:
context-{2:2}
locks held by syz-executor363/5622: 4, last CPU#0:
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: __simple_recursive_removal+0x19a/0x520 fs/libfs.c:619
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
#2: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rtlock_slowlock_locked+0x2ab/0x3c20 kernel/locking/rtmutex.c:1874
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1be/0x990 arch/x86/kvm/xen.c:1827
stack backtrace:
CPU: 0 UID: 0 PID: 5622 Comm: syz-executor363 Tainted: G W syzkaller #0 PREEMPT_{RT,(full)}
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_lock_invalid_wait_context kernel/locking/lockdep.c:4846 [inline]
check_wait_context kernel/locking/lockdep.c:4918 [inline]
__lock_acquire+0xef0/0x2e40 kernel/locking/lockdep.c:5204
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5906
rt_read_lock+0xcc/0x4b0 kernel/locking/spinlock_rt.c:249
kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x3a0/0xaf0 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x44a/0x900 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:rt_mutex_owner include/linux/rtmutex.h:52 [inline]
RIP: 0010:rtmutex_spin_on_owner kernel/locking/rtmutex.c:1504 [inline]
RIP: 0010:rtlock_slowlock_locked+0x34e5/0x3c20 kernel/locking/rtmutex.c:1893
Code: 80 3c 01 00 4c 8b b4 24 80 00 00 00 4c 8b 2c 24 74 08 4c 89 ef e8 db 0e df f6 48 8d 84 24 60 01 00 00 49 39 45 00 75 6c f3 90 <48> b8 00 00 00 00 00 fc ff df 48 8b 8c 24 a8 00 00 00 80 3c 01 00
RSP: 0018:ffffc90004e6f7a0 EFLAGS: 00000246
RAX: ffffc90004e6f900 RBX: 1ffff11006ff9bbe RCX: 1ffffffff1ca7871
RDX: 00000000e6b90d15 RSI: ffffffff8bcbd060 RDI: 0000000000000001
RBP: ffffc90004e6f9f0 R08: 1d00000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8e3c3880 R12: ffff888037fcddc0
R13: ffffffff8e53c388 R14: ffffffff8e53c390 R15: 1ffff11006ff9bba
rtlock_slowlock kernel/locking/rtmutex.c:1922 [inline]
rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
__rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
rt_spin_lock+0x165/0x400 kernel/locking/spinlock_rt.c:57
spin_lock include/linux/spinlock_rt.h:45 [inline]
simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
__simple_recursive_removal+0x215/0x520 fs/libfs.c:623
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:781
kvm_destroy_vm_debugfs virt/kvm/kvm_main.c:988 [inline]
kvm_destroy_vm virt/kvm/kvm_main.c:1261 [inline]
kvm_put_kvm+0x147/0xae0 virt/kvm/kvm_main.c:1331
kvm_vm_release+0x46/0x50 virt/kvm/kvm_main.c:1354
__fput+0x42a/0xa80 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x73a/0x2360 kernel/exit.c:1009
do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
__do_sys_exit_group kernel/exit.c:1163 [inline]
__se_sys_exit_group kernel/exit.c:1161 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1161
x64_sys_call+0x18bf/0x18c0 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f132ec60d05
Code: Unable to access opcode bytes at 0x7f132ec60cdb.
RSP: 002b:00007ffe413e3968 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f132ec60d05
RDX: 00000000000000e7 RSI: ffffffffffffffd8 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000009 R11: 0000000000000202 R12: 0000000000000000
R13: 00007f132ecfa118 R14: 00007f132ecfc3c8 R15: 00007f132ecfc3e0
</TASK>
----------------
Code disassembly (best guess):
0: 80 3c 01 00 cmpb $0x0,(%rcx,%rax,1)
4: 4c 8b b4 24 80 00 00 mov 0x80(%rsp),%r14
b: 00
c: 4c 8b 2c 24 mov (%rsp),%r13
10: 74 08 je 0x1a
12: 4c 89 ef mov %r13,%rdi
15: e8 db 0e df f6 call 0xf6df0ef5
1a: 48 8d 84 24 60 01 00 lea 0x160(%rsp),%rax
21: 00
22: 49 39 45 00 cmp %rax,0x0(%r13)
26: 75 6c jne 0x94
28: f3 90 pause
* 2a: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax <-- trapping instruction
31: fc ff df
34: 48 8b 8c 24 a8 00 00 mov 0xa8(%rsp),%rcx
3b: 00
3c: 80 3c 01 00 cmpb $0x0,(%rcx,%rax,1)
Strategy: The environment probe confirms that `/dev/kvm` is accessible and the basic KVM setup works. We can now proceed to generate the full C reproducer.
### Bug Analysis
The bug is a "sleeping function called from invalid context" in `kvm_xen_set_evtchn_fast()`, which occurs on `PREEMPT_RT` kernels.
1. The Xen timer is armed via the `KVM_XEN_VCPU_SET_ATTR` ioctl.
2. If the timer's expiration time is in the future, KVM arms an asynchronous hrtimer (`HRTIMER_MODE_ABS_HARD`).
3. When the timer expires, `xen_timer_callback()` executes in **hardirq context**.
4. The callback invokes `kvm_xen_set_evtchn_fast()`, which attempts to acquire `gpc->lock` (a `rwlock_t`).
5. On `PREEMPT_RT`, `rwlock_t` is mapped to a sleeping lock (`rt_rw_lock`). Acquiring a sleeping lock in hardirq context is invalid and triggers the BUG.
### Reproduction Strategy
To trigger the bug, we just need to arm the Xen timer with an expiration time safely in the future (e.g., 1 second) so that it fires asynchronously in hardirq context.
Please generate the C reproducer using the following step-by-step instructions:
1. **Include Headers**: Include `<fcntl.h>`, `<sys/ioctl.h>`, `<linux/kvm.h>`, `<stdint.h>`, `<unistd.h>`, and `<stdio.h>`.
2. **Define Constants**: Define `KVM_XEN_VCPU_ATTR_TYPE_TIMER` as `0x7` and `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL` as `((uint32_t)(-1))` to ensure compatibility with older headers.
3. **Define Attribute Struct**: Define a local version of the Xen VCPU attribute struct to avoid missing definitions in older kernel headers:
```c
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
#define MY_KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
```
4. **KVM Setup**: In `main()`, open `/dev/kvm`, create a VM (`KVM_CREATE_VM`), and create a VCPU (`KVM_CREATE_VCPU`).
5. **Arm the Timer**:
- Initialize the `my_kvm_xen_vcpu_attr` struct to zero.
- Set `type` to `KVM_XEN_VCPU_ATTR_TYPE_TIMER`.
- Set `u.timer.port` to `1`.
- Set `u.timer.priority` to `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL`.
- Set `u.timer.expires_ns` to `1000000000ULL` (1 second).
- Call `ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr)`.
6. **Wait for Execution**: Add `sleep(2);` at the end of `main()` to keep the process alive long enough for the hrtimer to fire in the background and trigger the bug.
Previous Reproducer Attempt:
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
int main(void)
{
int fd = open("/dev/kvm", O_RDWR);
if (fd < 0) {
printf("[-] Failed to open /dev/kvm: %s\n", strerror(errno));
exit(1);
}
printf("[+] open /dev/kvm successful.\n");
close(fd);
return 0;
}
Execution Results & Debugging Feedback:
The environment probe was successful. `/dev/kvm` is accessible. Please proceed to generate the full reproducer in the next iteration.
|
| 108/4 |
2026/08/12 13:26 |
llm |
repro-generator |
0m
Model:
Tokens:
input: 10483
output: 972
thoughts: 3305
Thoughts: **Reproducing the KVM Xen Timer Bug**
My primary objective here is to construct a C program that can reliably trigger the specific bug reported: "BUG: sleeping function called from invalid context in kvm_xen_set_evtchn_fast". To achieve this, I'm following a clear, step-by-step strategy outlined for me.
First, I know I'll need a comprehensive set of standard and Linux-specific headers. This includes `<fcntl.h>` for file control, `<sys/ioctl.h>` for I/O control operations, `<linux/kvm.h>` for KVM definitions, and others like `<stdint.h>`, `<unistd.h>`, `<stdio.h>`, `<stdlib.h>`, `<string.h>`, and `<errno.h>` for general programming and error handling.
Next, I need to define a couple of crucial constants. The bug report points to `KVM_XEN_VCPU_ATTR_TYPE_TIMER` being `0x7`, and a specific priority value, `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL`, which is defined as `((uint32_t)(-1))`. These will be fundamental for configuring the Xen timer attributes.
A key component will be defining a custom structure that mirrors the expected KVM Xen VCPU attributes, specifically for timer-related settings. I'll name it `struct my_kvm_xen_vcpu_attr`. This structure needs to accommodate the `type` and a union for various attribute types, including the `timer` structure with its `port`, `priority`, and `expires_ns` fields. I also need to define the `MY_KVM_XEN_VCPU_SET_ATTR` ioctl command, which will be used to pass this attribute structure to the kernel. I'll derive this from the `KVMIO` base and a specific command number, `0xcb`.
The core of the program involves setting up the KVM environment. This means opening the KVM device file (`/dev/kvm`), then using `ioctl` with `KVM_CREATE_VM` to create a virtual machine, and subsequently `KVM_CREATE_VCPU` to create a virtual CPU for that VM. Each of these steps needs error checking, of course, as failures here would prevent further progress.
The critical part is arming the Xen timer. The strategy specifies setting the `type` to `KVM_XEN_VCPU_ATTR_TYPE_TIMER`. For the timer's union members, I need to set `u.timer.port` to `1` and `u.timer.priority` to the predefined `KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL`. The most crucial setting is `u.timer.expires_ns`. The instruction is to set it to `1000000000ULL`, which represents 1 second.
Now, a brief internal debate arises regarding `expires_ns`. The strategy states "Set u.timer.expires_ns to 1000000000ULL (1 second)." My initial thought is whether this is an absolute or relative time. If it's absolute and the system uptime is already past 1 second, it might fire immediately, potentially not in the desired asynchronous hardirq context. However, I recall that KVM's guest clock often starts at zero upon VM creation. This means `1000000000ULL` will indeed represent exactly one second into the *guest's* future, which aligns perfectly with the bug's requirement for it to fire asynchronously later. Therefore, I'll stick to the specified value, confident it will work as intended in the VM's context.
After configuring the `attr` structure with these timer details, I'll execute the `ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr)` call. This is the action that should, according to the bug report, trigger the problematic kernel path.
Finally, to give the timer a chance to fire and trigger the bug, I'll introduce a `sleep(2);` call. This ensures that at least two seconds pass, which is more than enough time for the 1-second timer to expire and execute its callback. Once the sleep is over, I'll clean up by closing the file descriptors for the VCPU, VM, and KVM device.
I've also considered whether any explicit Xen enablement via `KVM_ENABLE_CAP` might be necessary, but the provided strategy doesn't mention it, so I'll proceed with the direct `KVM_XEN_VCPU_SET_ATTR` ioctl, assuming it works within the standard KVM setup.
With this plan, I'm ready to generate the C code that implements these precise steps.
|
| 109/4 |
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tool |
set-results |
0m
Args: map[IsProbe:false RawCandidateReproC:#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
#define KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL ((uint32_t)(-1))
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
#define MY_KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
int main(void)
{
int kvm_fd, vm_fd, vcpu_fd;
struct my_kvm_xen_vcpu_attr attr;
int res;
kvm_fd = open("/dev/kvm", O_RDWR);
if (kvm_fd < 0) {
printf("[-] Failed to open /dev/kvm: %s\n", strerror(errno));
exit(1);
}
printf("[+] open /dev/kvm successful.\n");
vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0);
if (vm_fd < 0) {
printf("[-] Failed to KVM_CREATE_VM: %s\n", strerror(errno));
exit(1);
}
printf("[+] KVM_CREATE_VM successful.\n");
vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);
if (vcpu_fd < 0) {
printf("[-] Failed to KVM_CREATE_VCPU: %s\n", strerror(errno));
exit(1);
}
printf("[+] KVM_CREATE_VCPU successful.\n");
memset(&attr, 0, sizeof(attr));
attr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
attr.u.timer.port = 1;
attr.u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
attr.u.timer.expires_ns = 1000000000ULL;
res = ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr);
if (res < 0) {
printf("[-] Failed to MY_KVM_XEN_VCPU_SET_ATTR: %s\n", strerror(errno));
exit(1);
}
printf("[+] MY_KVM_XEN_VCPU_SET_ATTR successful.\n");
printf("[+] Waiting for timer to fire...\n");
sleep(2);
close(vcpu_fd);
close(vm_fd);
close(kvm_fd);
printf("[+] Done.\n");
return 0;
}
]
Results: map[IsProbe:false RawCandidateReproC:#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
#define KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL ((uint32_t)(-1))
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
#define MY_KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
int main(void)
{
int kvm_fd, vm_fd, vcpu_fd;
struct my_kvm_xen_vcpu_attr attr;
int res;
kvm_fd = open("/dev/kvm", O_RDWR);
if (kvm_fd < 0) {
printf("[-] Failed to open /dev/kvm: %s\n", strerror(errno));
exit(1);
}
printf("[+] open /dev/kvm successful.\n");
vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0);
if (vm_fd < 0) {
printf("[-] Failed to KVM_CREATE_VM: %s\n", strerror(errno));
exit(1);
}
printf("[+] KVM_CREATE_VM successful.\n");
vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);
if (vcpu_fd < 0) {
printf("[-] Failed to KVM_CREATE_VCPU: %s\n", strerror(errno));
exit(1);
}
printf("[+] KVM_CREATE_VCPU successful.\n");
memset(&attr, 0, sizeof(attr));
attr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
attr.u.timer.port = 1;
attr.u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
attr.u.timer.expires_ns = 1000000000ULL;
res = ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr);
if (res < 0) {
printf("[-] Failed to MY_KVM_XEN_VCPU_SET_ATTR: %s\n", strerror(errno));
exit(1);
}
printf("[+] MY_KVM_XEN_VCPU_SET_ATTR successful.\n");
printf("[+] Waiting for timer to fire...\n");
sleep(2);
close(vcpu_fd);
close(vm_fd);
close(kvm_fd);
printf("[+] Done.\n");
return 0;
}
]
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loop |
|
0m
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iteration |
0 |
0m
|
| 112/5 |
2026/08/12 13:26 |
action |
merge-repro-c |
0m
Results: map[CurrentCandidateReproC:#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
#define KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL ((uint32_t)(-1))
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
#define MY_KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
int main(void)
{
int kvm_fd, vm_fd, vcpu_fd;
struct my_kvm_xen_vcpu_attr attr;
int res;
kvm_fd = open("/dev/kvm", O_RDWR);
if (kvm_fd < 0) {
printf("[-] Failed to open /dev/kvm: %s\n", strerror(errno));
exit(1);
}
printf("[+] open /dev/kvm successful.\n");
vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0);
if (vm_fd < 0) {
printf("[-] Failed to KVM_CREATE_VM: %s\n", strerror(errno));
exit(1);
}
printf("[+] KVM_CREATE_VM successful.\n");
vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);
if (vcpu_fd < 0) {
printf("[-] Failed to KVM_CREATE_VCPU: %s\n", strerror(errno));
exit(1);
}
printf("[+] KVM_CREATE_VCPU successful.\n");
memset(&attr, 0, sizeof(attr));
attr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
attr.u.timer.port = 1;
attr.u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
attr.u.timer.expires_ns = 1000000000ULL;
res = ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr);
if (res < 0) {
printf("[-] Failed to MY_KVM_XEN_VCPU_SET_ATTR: %s\n", strerror(errno));
exit(1);
}
printf("[+] MY_KVM_XEN_VCPU_SET_ATTR successful.\n");
printf("[+] Waiting for timer to fire...\n");
sleep(2);
close(vcpu_fd);
close(vm_fd);
close(kvm_fd);
printf("[+] Done.\n");
return 0;
}
]
|
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action |
compile-c-prog |
0m
Results: map[CompilerError: FormattedReproC:#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
#define KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL ((uint32_t)(-1))
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
#define MY_KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
int main(void)
{
int kvm_fd, vm_fd, vcpu_fd;
struct my_kvm_xen_vcpu_attr attr;
int res;
kvm_fd = open("/dev/kvm", O_RDWR);
if (kvm_fd < 0) {
printf("[-] Failed to open /dev/kvm: %s\n", strerror(errno));
exit(1);
}
printf("[+] open /dev/kvm successful.\n");
vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0);
if (vm_fd < 0) {
printf("[-] Failed to KVM_CREATE_VM: %s\n", strerror(errno));
exit(1);
}
printf("[+] KVM_CREATE_VM successful.\n");
vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);
if (vcpu_fd < 0) {
printf("[-] Failed to KVM_CREATE_VCPU: %s\n", strerror(errno));
exit(1);
}
printf("[+] KVM_CREATE_VCPU successful.\n");
memset(&attr, 0, sizeof(attr));
attr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
attr.u.timer.port = 1;
attr.u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
attr.u.timer.expires_ns = 1000000000ULL;
res = ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr);
if (res < 0) {
printf("[-] Failed to MY_KVM_XEN_VCPU_SET_ATTR: %s\n", strerror(errno));
exit(1);
}
printf("[+] MY_KVM_XEN_VCPU_SET_ATTR successful.\n");
printf("[+] Waiting for timer to fire...\n");
sleep(2);
close(vcpu_fd);
close(vm_fd);
close(kvm_fd);
printf("[+] Done.\n");
return 0;
}
]
|
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action |
If |
0m
Args:
|
| 115/3 |
2026/08/12 13:26 |
action |
run-c-repro |
2m
Results: map[CandidateBugTitle:WARNING: locking bug in kvm_xen_set_evtchn_fast CandidateCrashReport:=============================
[ BUG: Invalid wait context ]
syzkaller #1 Not tainted
-----------------------------
swapper/0/0 is trying to lock:
ffff88810d699bb0 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x9a0 arch/x86/kvm/xen.c:1829
other info that might help us debug this:
context-{2:2}
locks held by swapper/0/0: 1, last CPU#0:
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1bc/0x9a0 arch/x86/kvm/xen.c:1827
stack backtrace:
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #1 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_lock_invalid_wait_context kernel/locking/lockdep.c:4846 [inline]
check_wait_context kernel/locking/lockdep.c:4918 [inline]
__lock_acquire+0xef0/0x2e50 kernel/locking/lockdep.c:5204
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5906
__raw_read_lock_irqsave include/linux/rwlock_api_smp.h:174 [inline]
_raw_read_lock_irqsave+0x48/0x60 kernel/locking/spinlock.c:240
kvm_xen_set_evtchn_fast+0x1f4/0x9a0 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x371/0xa10 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x448/0x910 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64
Code: 8d 8f 02 e9 d3 03 03 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d b3 65 15 00 fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
RSP: 0018:ffffffff8e807ca0 EFLAGS: 00000246
RAX: 00000000001183f3 RBX: ffffffff819a214c RCX: 0000000080000001
RDX: 0000000000000001 RSI: ffffffff8e176c40 RDI: ffffffff8c326480
RBP: ffffffff8e807d78 R08: ffff8881386338db R09: 1ffff110270c671b
R10: dffffc0000000000 R11: ffffed10270c671c R12: 0000000000000000
R13: 1ffffffff1d11e20 R14: 1ffffffff1d00f9c R15: dffffc0000000000
arch_safe_halt arch/x86/kernel/process.c:767 [inline]
default_idle+0x9/0x20 arch/x86/kernel/process.c:768
default_idle_call+0x72/0xb0 kernel/sched/idle.c:122
cpuidle_idle_call kernel/sched/idle.c:199 [inline]
do_idle+0x1cc/0x540 kernel/sched/idle.c:355
cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:454
rest_init+0x378/0x3a0 init/main.c:727
start_kernel+0x392/0x3e0 init/main.c:1185
x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291
common_startup_64+0x13e/0x157
</TASK>
----------------
Code disassembly (best guess):
0: 8d 8f 02 e9 d3 03 lea 0x3d3e902(%rdi),%ecx
6: 03 00 add (%rax),%eax
8: cc int3
9: cc int3
a: cc int3
b: 90 nop
c: 90 nop
d: 90 nop
e: 90 nop
f: 90 nop
10: 90 nop
11: 90 nop
12: 90 nop
13: 90 nop
14: 90 nop
15: 90 nop
16: 90 nop
17: 90 nop
18: 90 nop
19: 90 nop
1a: 90 nop
1b: f3 0f 1e fa endbr64
1f: 66 90 xchg %ax,%ax
21: 0f 00 2d b3 65 15 00 verw 0x1565b3(%rip) # 0x1565db
28: fb sti
29: f4 hlt
* 2a: c3 ret <-- trapping instruction
2b: cc int3
2c: cc int3
2d: cc int3
2e: cc int3
2f: cc int3
30: cc int3
31: cc int3
32: cc int3
33: cc int3
34: cc int3
35: cc int3
36: cc int3
37: cc int3
38: cc int3
39: cc int3
3a: cc int3
3b: 90 nop
3c: 90 nop
3d: 90 nop
3e: 90 nop
3f: 90 nop
CandidateReproduced:true ConsoleOutput:[ 115.887758][ T33] kauditd_printk_skb: 10 callbacks suppressed
[ 115.887775][ T33] audit: type=1400 audit(1786541327.763:201): avc: denied { transition } for pid=5829 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 115.905432][ T33] audit: type=1400 audit(1786541327.763:202): avc: denied { noatsecure } for pid=5829 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 115.917204][ T33] audit: type=1400 audit(1786541327.763:203): avc: denied { rlimitinh } for pid=5829 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 115.928355][ T33] audit: type=1400 audit(1786541327.763:204): avc: denied { siginh } for pid=5829 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 117.731131][ T33] audit: type=1400 audit(1786541329.603:205): avc: denied { write } for pid=5834 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 117.816274][ T33] audit: type=1400 audit(1786541329.693:206): avc: denied { write } for pid=5837 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 117.953117][ T33] audit: type=1400 audit(1786541329.823:207): avc: denied { write } for pid=5840 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 118.045447][ T33] audit: type=1400 audit(1786541329.923:208): avc: denied { write } for pid=5843 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.273939][ T33] audit: type=1400 audit(1786541332.143:209): avc: denied { write } for pid=5847 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.403671][ T33] audit: type=1400 audit(1786541332.273:210): avc: denied { write } for pid=5850 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.910529][ T33] kauditd_printk_skb: 2 callbacks suppressed
[ 120.910547][ T33] audit: type=1400 audit(1786541332.783:213): avc: denied { write } for pid=5859 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.003224][ T33] audit: type=1400 audit(1786541332.873:214): avc: denied { write } for pid=5862 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.396060][ T33] audit: type=1400 audit(1786541333.273:215): avc: denied { write } for pid=5867 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.570187][ T33] audit: type=1400 audit(1786541333.443:216): avc: denied { write } for pid=5870 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.157900][ T33] audit: type=1400 audit(1786541334.023:217): avc: denied { write } for pid=5877 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.243198][ T33] audit: type=1400 audit(1786541334.113:218): avc: denied { write } for pid=5880 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 123.158549][ T33] audit: type=1400 audit(1786541335.033:219): avc: denied { write } for pid=5887 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 123.241477][ T33] audit: type=1400 audit(1786541335.113:220): avc: denied { write } for pid=5890 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:63790' (ED25519) to the list of known hosts.
[ 125.523473][ T33] audit: type=1400 audit(1786541337.393:221): avc: denied { read write } for pid=5901 comm="syz-executor877" name="kvm" dev="devtmpfs" ino=84 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:kvm_device_t tclass=chr_file permissive=1
[ 125.544929][ T33] audit: type=1400 audit(1786541337.413:222): avc: denied { open } for pid=5901 comm="syz-executor877" path="/dev/kvm" dev="devtmpfs" ino=84 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:kvm_device_t tclass=chr_file permissive=1
[ 126.538020][ C0]
[ 126.539160][ C0] =============================
[ 126.541225][ C0] [ BUG: Invalid wait context ]
[ 126.543376][ C0] syzkaller #1 Not tainted
[ 126.545415][ C0] -----------------------------
[ 126.548095][ C0] swapper/0/0 is trying to lock:
[ 126.551037][ C0] ffff88810d699bb0 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x9a0
[ 126.556554][ C0] other info that might help us debug this:
[ 126.560200][ C0] context-{2:2}
[ 126.562828][ C0] locks held by swapper/0/0: 1, last CPU#0:
[ 126.566268][ C0] #0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1bc/0x9a0
[ 126.571522][ C0] stack backtrace:
[ 126.573855][ C0] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #1 PREEMPT(full)
[ 126.573874][ C0] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 126.573883][ C0] Call Trace:
[ 126.573891][ C0] <IRQ>
[ 126.573912][ C0] dump_stack_lvl+0xe8/0x150
[ 126.573937][ C0] __lock_acquire+0xef0/0x2e50
[ 126.573957][ C0] ? __lock_acquire+0x6df/0x2e50
[ 126.573974][ C0] lock_acquire+0x115/0x350
[ 126.573988][ C0] ? kvm_xen_set_evtchn_fast+0x1f4/0x9a0
[ 126.574010][ C0] ? xa_load+0x1db/0x210
[ 126.574029][ C0] _raw_read_lock_irqsave+0x48/0x60
[ 126.574042][ C0] ? kvm_xen_set_evtchn_fast+0x1f4/0x9a0
[ 126.574058][ C0] kvm_xen_set_evtchn_fast+0x1f4/0x9a0
[ 126.574078][ C0] ? kvm_xen_set_evtchn_fast+0x1bc/0x9a0
[ 126.574097][ C0] xen_timer_callback+0x109/0x220
[ 126.574117][ C0] ? __pfx_xen_timer_callback+0x10/0x10
[ 126.574137][ C0] __hrtimer_run_queues+0x371/0xa10
[ 126.574163][ C0] hrtimer_interrupt+0x448/0x910
[ 126.574190][ C0] __sysvec_apic_timer_interrupt+0x102/0x430
[ 126.574211][ C0] sysvec_apic_timer_interrupt+0xa1/0xc0
[ 126.574226][ C0] </IRQ>
[ 126.574230][ C0] <TASK>
[ 126.574236][ C0] asm_sysvec_apic_timer_interrupt+0x1a/0x20
[ 126.574252][ C0] RIP: 0010:pv_native_safe_halt+0xf/0x20
[ 126.574268][ C0] Code: 8d 8f 02 e9 d3 03 03 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d b3 65 15 00 fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
[ 126.574280][ C0] RSP: 0018:ffffffff8e807ca0 EFLAGS: 00000246
[ 126.574293][ C0] RAX: 00000000001183f3 RBX: ffffffff819a214c RCX: 0000000080000001
[ 126.574304][ C0] RDX: 0000000000000001 RSI: ffffffff8e176c40 RDI: ffffffff8c326480
[ 126.574313][ C0] RBP: ffffffff8e807d78 R08: ffff8881386338db R09: 1ffff110270c671b
[ 126.574323][ C0] R10: dffffc0000000000 R11: ffffed10270c671c R12: 0000000000000000
[ 126.574332][ C0] R13: 1ffffffff1d11e20 R14: 1ffffffff1d00f9c R15: dffffc0000000000
[ 126.574396][ C0] ? do_idle+0x1cc/0x540
[ 126.574414][ C0] default_idle+0x9/0x20
[ 126.574430][ C0] default_idle_call+0x72/0xb0
[ 126.574446][ C0] do_idle+0x1cc/0x540
[ 126.574459][ C0] ? __pfx_do_idle+0x10/0x10
[ 126.574473][ C0] cpu_startup_entry+0x43/0x60
[ 126.574484][ C0] rest_init+0x378/0x3a0
[ 126.574502][ C0] ? __pfx_rest_init+0x10/0x10
[ 126.574521][ C0] ? __pfx_kernel_init+0x10/0x10
[ 126.574540][ C0] ? acpi_ut_status_exit+0x120/0x1f0
[ 126.574563][ C0] ? acpi_ut_status_exit+0x120/0x1f0
[ 126.574585][ C0] ? acpi_enable_subsystem+0x286/0x3c0
[ 126.574601][ C0] start_kernel+0x392/0x3e0
[ 126.574615][ C0] x86_64_start_reservations+0x24/0x30
[ 126.574635][ C0] x86_64_start_kernel+0x137/0x1b0
[ 126.574653][ C0] common_startup_64+0x13e/0x157
[ 126.574677][ C0] </TASK>
[+] open /dev/kvm successful.
[+] KVM_CREATE_VM successful.
[+] KVM_CREATE_VCPU successful.
[+] MY_KVM_XEN_VCPU_SET_ATTR successful.
[+] Waiting for timer to fire...
[+] Done.
[ 134.339652][ T1376] ieee802154 phy0 wpan0: encryption failed: -22
[ 134.342962][ T1376] ieee802154 phy1 wpan1: encryption failed: -22
OtherCrashReports:<nil> StraceOutput: TestError:]
|
| 116/3 |
2026/08/12 13:29 |
action |
truncate-log |
0m
Results: map[TruncatedConsoleOutput:[ 115.887758][ T33] kauditd_printk_skb: 10 callbacks suppressed
[ 115.887775][ T33] audit: type=1400 audit(1786541327.763:201): avc: denied { transition } for pid=5829 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 115.905432][ T33] audit: type=1400 audit(1786541327.763:202): avc: denied { noatsecure } for pid=5829 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 115.917204][ T33] audit: type=1400 audit(1786541327.763:203): avc: denied { rlimitinh } for pid=5829 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 115.928355][ T33] audit: type=1400 audit(1786541327.763:204): avc: denied { siginh } for pid=5829 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 117.731131][ T33] audit: type=1400 audit(1786541329.603:205): avc: denied { write } for pid=5834 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 117.816274][ T33] audit: type=1400 audit(1786541329.693:206): avc: denied { write } for pid=5837 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 117.953117][ T33] audit: type=1400 audit(1786541329.823:207): avc: denied { write } for pid=5840 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 118.045447][ T33] audit: type=1400 audit(1786541329.923:208): avc: denied { write } for pid=5843 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.273939][ T33] audit: type=1400 audit(1786541332.143:209): avc: denied { write } for pid=5847 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.403671][ T33] audit: type=1400 audit(1786541332.273:210): avc: denied { write } for pid=5850 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.910529][ T33] kauditd_printk_skb: 2 callbacks suppressed
[ 120.910547][ T33] audit: type=1400 audit(1786541332.783:213): avc: denied { write } for pid=5859 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.003224][ T33] audit: type=1400 audit(1786541332.873:214): avc: denied { write } for pid=5862 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.396060][ T33] audit: type=1400 audit(1786541333.273:215): avc: denied { write } for pid=5867 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.570187][ T33] audit: type=1400 audit(1786541333.443:216): avc: denied { write } for pid=5870 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.157900][ T33] audit: type=1400 audit(1786541334.023:217): avc: denied { write } for pid=5877 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.243198][ T33] audit: type=1400 audit(1786541334.113:218): avc: denied { write } for pid=5880 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 123.158549][ T33] audit: type=1400 audit(1786541335.033:219): avc: denied { write } for pid=5887 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 123.241477][ T33] audit: type=1400 audit(1786541335.113:220): avc: denied { write } for pid=5890 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:63790' (ED25519) to the list of known hosts.
[ 125.523473][ T33] audit: type=1400 audit(1786541337.393:221): avc: denied { read write } for pid=5901 comm="syz-executor877" name="kvm" dev="devtmpfs" ino=84 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:kvm_device_t tclass=chr_file permissive=1
[ 125.544929][ T33] audit: type=1400 audit(1786541337.413:222): avc: denied { open } for pid=5901 comm="syz-executor877" path="/dev/kvm" dev="devtmpfs" ino=84 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:kvm_device_t tclass=chr_file permissive=1
[ 126.538020][ C0]
[ 126.539160][ C0] =============================
[ 126.541225][ C0] [ BUG: Invalid wait context ]
[ 126.543376][ C0] syzkaller #1 Not tainted
[ 126.545415][ C0] -----------------------------
[ 126.548095][ C0] swapper/0/0 is trying to lock:
[ 126.551037][ C0] ffff88810d699bb0 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x9a0
[ 126.556554][ C0] other info that might help us debug this:
[ 126.560200][ C0] context-{2:2}
[ 126.562828][ C0] locks held by swapper/0/0: 1, last CPU#0:
[ 126.566268][ C0] #0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1bc/0x9a0
[ 126.571522][ C0] stack backtrace:
[ 126.573855][ C0] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #1 PREEMPT(full)
[ 126.573874][ C0] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 126.573883][ C0] Call Trace:
[ 126.573891][ C0] <IRQ>
[ 126.573912][ C0] dump_stack_lvl+0xe8/0x150
[ 126.573937][ C0] __lock_acquire+0xef0/0x2e50
[ 126.573957][ C0] ? __lock_acquire+0x6df/0x2e50
[ 126.573974][ C0] lock_acquire+0x115/0x350
[ 126.573988][ C0] ? kvm_xen_set_evtchn_fast+0x1f4/0x9a0
[ 126.574010][ C0] ? xa_load+0x1db/0x210
[ 126.574029][ C0] _raw_read_lock_irqsave+0x48/0x60
[ 126.574042][ C0] ? kvm_xen_set_evtchn_fast+0x1f4/0x9a0
[ 126.574058][ C0] kvm_xen_set_evtchn_fast+0x1f4/0x9a0
[ 126.574078][ C0] ? kvm_xen_set_evtchn_fast+0x1bc/0x9a0
[ 126.574097][ C0] xen_timer_callback+0x109/0x220
[ 126.574117][ C0] ? __pfx_xen_timer_callback+0x10/0x10
[ 126.574137][ C0] __hrtimer_run_queues+0x371/0xa10
[ 126.574163][ C0] hrtimer_interrupt+0x448/0x910
[ 126.574190][ C0] __sysvec_apic_timer_interrupt+0x102/0x430
[ 126.574211][ C0] sysvec_apic_timer_interrupt+0xa1/0xc0
[ 126.574226][ C0] </IRQ>
[ 126.574230][ C0] <TASK>
[ 126.574236][ C0] asm_sysvec_apic_timer_interrupt+0x1a/0x20
[ 126.574252][ C0] RIP: 0010:pv_native_safe_halt+0xf/0x20
[ 126.574268][ C0] Code: 8d 8f 02 e9 d3 03 03 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d b3 65 15 00 fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
[ 126.574280][ C0] RSP: 0018:ffffffff8e807ca0 EFLAGS: 00000246
[ 126.574293][ C0] RAX: 00000000001183f3 RBX: ffffffff819a214c RCX: 0000000080000001
[ 126.574304][ C0] RDX: 0000000000000001 RSI: ffffffff8e176c40 RDI: ffffffff8c326480
[ 126.574313][ C0] RBP: ffffffff8e807d78 R08: ffff8881386338db R09: 1ffff110270c671b
[ 126.574323][ C0] R10: dffffc0000000000 R11: ffffed10270c671c R12: 0000000000000000
[ 126.574332][ C0] R13: 1ffffffff1d11e20 R14: 1ffffffff1d00f9c R15: dffffc0000000000
[ 126.574396][ C0] ? do_idle+0x1cc/0x540
[ 126.574414][ C0] default_idle+0x9/0x20
[ 126.574430][ C0] default_idle_call+0x72/0xb0
[ 126.574446][ C0] do_idle+0x1cc/0x540
[ 126.574459][ C0] ? __pfx_do_idle+0x10/0x10
[ 126.574473][ C0] cpu_startup_entry+0x43/0x60
[ 126.574484][ C0] rest_init+0x378/0x3a0
[ 126.574502][ C0] ? __pfx_rest_init+0x10/0x10
[ 126.574521][ C0] ? __pfx_kernel_init+0x10/0x10
[ 126.574540][ C0] ? acpi_ut_status_exit+0x120/0x1f0
[ 126.574563][ C0] ? acpi_ut_status_exit+0x120/0x1f0
[ 126.574585][ C0] ? acpi_enable_subsystem+0x286/0x3c0
[ 126.574601][ C0] start_kernel+0x392/0x3e0
[ 126.574615][ C0] x86_64_start_reservations+0x24/0x30
[ 126.574635][ C0] x86_64_start_kernel+0x137/0x1b0
[ 126.574653][ C0] common_startup_64+0x13e/0x157
[ 126.574677][ C0] </TASK>
[+] open /dev/kvm successful.
[+] KVM_CREATE_VM successful.
[+] KVM_CREATE_VCPU successful.
[+] MY_KVM_XEN_VCPU_SET_ATTR successful.
[+] Waiting for timer to fire...
[+] Done.
[ 134.339652][ T1376] ieee802154 phy0 wpan0: encryption failed: -22
[ 134.342962][ T1376] ieee802154 phy1 wpan1: encryption failed: -22
TruncatedCrashReport:=============================
[ BUG: Invalid wait context ]
syzkaller #1 Not tainted
-----------------------------
swapper/0/0 is trying to lock:
ffff88810d699bb0 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x9a0 arch/x86/kvm/xen.c:1829
other info that might help us debug this:
context-{2:2}
locks held by swapper/0/0: 1, last CPU#0:
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1bc/0x9a0 arch/x86/kvm/xen.c:1827
stack backtrace:
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #1 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_lock_invalid_wait_context kernel/locking/lockdep.c:4846 [inline]
check_wait_context kernel/locking/lockdep.c:4918 [inline]
__lock_acquire+0xef0/0x2e50 kernel/locking/lockdep.c:5204
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5906
__raw_read_lock_irqsave include/linux/rwlock_api_smp.h:174 [inline]
_raw_read_lock_irqsave+0x48/0x60 kernel/locking/spinlock.c:240
kvm_xen_set_evtchn_fast+0x1f4/0x9a0 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x371/0xa10 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x448/0x910 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64
Code: 8d 8f 02 e9 d3 03 03 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d b3 65 15 00 fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
RSP: 0018:ffffffff8e807ca0 EFLAGS: 00000246
RAX: 00000000001183f3 RBX: ffffffff819a214c RCX: 0000000080000001
RDX: 0000000000000001 RSI: ffffffff8e176c40 RDI: ffffffff8c326480
RBP: ffffffff8e807d78 R08: ffff8881386338db R09: 1ffff110270c671b
R10: dffffc0000000000 R11: ffffed10270c671c R12: 0000000000000000
R13: 1ffffffff1d11e20 R14: 1ffffffff1d00f9c R15: dffffc0000000000
arch_safe_halt arch/x86/kernel/process.c:767 [inline]
default_idle+0x9/0x20 arch/x86/kernel/process.c:768
default_idle_call+0x72/0xb0 kernel/sched/idle.c:122
cpuidle_idle_call kernel/sched/idle.c:199 [inline]
do_idle+0x1cc/0x540 kernel/sched/idle.c:355
cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:454
rest_init+0x378/0x3a0 init/main.c:727
start_kernel+0x392/0x3e0 init/main.c:1185
x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291
common_startup_64+0x13e/0x157
</TASK>
----------------
Code disassembly (best guess):
0: 8d 8f 02 e9 d3 03 lea 0x3d3e902(%rdi),%ecx
6: 03 00 add (%rax),%eax
8: cc int3
9: cc int3
a: cc int3
b: 90 nop
c: 90 nop
d: 90 nop
e: 90 nop
f: 90 nop
10: 90 nop
11: 90 nop
12: 90 nop
13: 90 nop
14: 90 nop
15: 90 nop
16: 90 nop
17: 90 nop
18: 90 nop
19: 90 nop
1a: 90 nop
1b: f3 0f 1e fa endbr64
1f: 66 90 xchg %ax,%ax
21: 0f 00 2d b3 65 15 00 verw 0x1565b3(%rip) # 0x1565db
28: fb sti
29: f4 hlt
* 2a: c3 ret <-- trapping instruction
2b: cc int3
2c: cc int3
2d: cc int3
2e: cc int3
2f: cc int3
30: cc int3
31: cc int3
32: cc int3
33: cc int3
34: cc int3
35: cc int3
36: cc int3
37: cc int3
38: cc int3
39: cc int3
3a: cc int3
3b: 90 nop
3c: 90 nop
3d: 90 nop
3e: 90 nop
3f: 90 nop
TruncatedStraceOutput:]
|
| 117/3 |
2026/08/12 13:29 |
agent |
repro-oracle |
0m
Model:
Results: map[Feedback:The reproducer successfully triggered the target bug. The crash report shows `[ BUG: Invalid wait context ]` with the exact same stack trace as the original report: `xen_timer_callback` -> `kvm_xen_set_evtchn_fast` -> lock acquisition. The original report was on a PREEMPT_RT kernel, which additionally triggered a "sleeping function called from invalid context" warning because spinlocks/rwlocks sleep in RT, but the underlying issue (taking `gpc->lock` in hardirq context from the hrtimer callback) is identical and caught by lockdep's wait context checks in both cases. ProbePassed:false TerminalError: TitleMatches:true]
Instruction: You are a security researcher with deep Linux kernel background.
Analyze the results of running the generated program.
=== CRITICAL ENVIRONMENT & TARGET CLASSIFICATION ===
Set 'TerminalError' to a descriptive error message ONLY if:
1. The execution failed due to missing hardware device nodes, subsystems, kernel modules, or privilege limits
that cannot be loaded, created, or bypassed by user-space C code edits in the VM guest.
2. The target source files or functions described in the bug description do not exist in the checked-out codebase,
meaning the codebase version is mismatched and the target code is absent.
=== CRITICAL PROHIBITIONS ===
- Do NOT classify a run as a terminal failure or assume a bug is fixed based on git log entries, commit titles,
or commit messages. Reproducibility can ONLY be determined by executing reproducer candidates in the VM.
- Do NOT suggest C code strategies, repairs, or namespace bypasses when setting 'TerminalError'.
=== PHASE 2: BUG REPRODUCTION (EVALUATION) ===
The executed program was a full reproducer candidate attempting to trigger the target bug/crash.
Use this to guide your classification and feedback:
1. If a crash was triggered (Reproduced is true):
- Determine if the triggered crash matches the expected bug.
- If you conclude they represent the same underlying bug (the same root cause)
despite different titles, crash signatures, or call traces, set TitleMatches
to true and provide a detailed, technical, and verbose explanation of the
equivalence in the 'Feedback' field.
- If they do not represent the same bug (a completely unrelated crash/collision),
set TitleMatches to false and explain the collision in 'Feedback'.
- If they match exactly, set TitleMatches to true and provide a brief confirmation in 'Feedback'.
2. If the execution was successful (exit 0) WITHOUT a crash (Reproduced is false):
- The reproduction attempt failed to trigger the bug. Analyze the console/strace output
to understand why the bug did not trigger (e.g., timing, input arguments, environment setup)
and provide feedback on how to improve the reproducer logic to trigger the crash.
Critical Diagnostic Rule for Reproduction Failures:
If the reproduction attempt fails (e.g., a system call returns an error, or a
warning/error message appears in the console log), you MUST:
1. Identify the failing system call from the execution trace or strace output.
2. Identify any corresponding warning or error messages in the console log.
3. Immediately search the kernel source tree for the warning message strings or
the code of the failing system call/subsystem to locate the validation logic.
4. Trace the kernel's validation logic to diagnose the exact constraint violation
or input mismatch in the generated program.
5. Provide a technical diagnosis in the feedback explaining the exact kernel constraint that was violated and why.
Prefer calling several tools at the same time to save round-trips.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt: Bug Description: BUG: sleeping function called from invalid context in kvm_xen_set_evtchn_fast
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:248
in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 5622, name: syz-executor363
preempt_count: 10000, expected: 0
RCU nest depth: 1, expected: 1
locks held by syz-executor363/5622: 4, last CPU#0:
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: __simple_recursive_removal+0x19a/0x520 fs/libfs.c:619
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
#2: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rtlock_slowlock_locked+0x2ab/0x3c20 kernel/locking/rtmutex.c:1874
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1be/0x990 arch/x86/kvm/xen.c:1827
irq event stamp: 13272
hardirqs last enabled at (13271): [<ffffffff8b53b4b3>] __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:187 [inline]
hardirqs last enabled at (13271): [<ffffffff8b53b4b3>] _raw_spin_unlock_irq+0x23/0x50 kernel/locking/spinlock.c:206
hardirqs last disabled at (13272): [<ffffffff8b501aee>] sysvec_apic_timer_interrupt+0xe/0xc0 arch/x86/kernel/apic/apic.c:1062
softirqs last enabled at (6940): [<ffffffff81882fe0>] __local_bh_enable_ip+0x1a0/0x2b0 kernel/softirq.c:305
softirqs last disabled at (6932): [<ffffffff891cda09>] local_bh_disable include/linux/bottom_half.h:20 [inline]
softirqs last disabled at (6932): [<ffffffff891cda09>] __alloc_skb+0x189/0x7a0 net/core/skbuff.c:697
Preemption disabled at:
[<ffffffff81883b8e>] irq_enter_rcu+0x1e/0x1f0 kernel/softirq.c:668
CPU: 0 UID: 0 PID: 5622 Comm: syz-executor363 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
__might_resched+0x329/0x480 kernel/sched/core.c:9194
rt_read_lock+0xa9/0x4b0 kernel/locking/spinlock_rt.c:248
kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x3a0/0xaf0 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x44a/0x900 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:rt_mutex_owner include/linux/rtmutex.h:52 [inline]
RIP: 0010:rtmutex_spin_on_owner kernel/locking/rtmutex.c:1504 [inline]
RIP: 0010:rtlock_slowlock_locked+0x34e5/0x3c20 kernel/locking/rtmutex.c:1893
Code: 80 3c 01 00 4c 8b b4 24 80 00 00 00 4c 8b 2c 24 74 08 4c 89 ef e8 db 0e df f6 48 8d 84 24 60 01 00 00 49 39 45 00 75 6c f3 90 <48> b8 00 00 00 00 00 fc ff df 48 8b 8c 24 a8 00 00 00 80 3c 01 00
RSP: 0018:ffffc90004e6f7a0 EFLAGS: 00000246
RAX: ffffc90004e6f900 RBX: 1ffff11006ff9bbe RCX: 1ffffffff1ca7871
RDX: 00000000e6b90d15 RSI: ffffffff8bcbd060 RDI: 0000000000000001
RBP: ffffc90004e6f9f0 R08: 1d00000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8e3c3880 R12: ffff888037fcddc0
R13: ffffffff8e53c388 R14: ffffffff8e53c390 R15: 1ffff11006ff9bba
rtlock_slowlock kernel/locking/rtmutex.c:1922 [inline]
rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
__rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
rt_spin_lock+0x165/0x400 kernel/locking/spinlock_rt.c:57
spin_lock include/linux/spinlock_rt.h:45 [inline]
simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
__simple_recursive_removal+0x215/0x520 fs/libfs.c:623
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:781
kvm_destroy_vm_debugfs virt/kvm/kvm_main.c:988 [inline]
kvm_destroy_vm virt/kvm/kvm_main.c:1261 [inline]
kvm_put_kvm+0x147/0xae0 virt/kvm/kvm_main.c:1331
kvm_vm_release+0x46/0x50 virt/kvm/kvm_main.c:1354
__fput+0x42a/0xa80 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x73a/0x2360 kernel/exit.c:1009
do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
__do_sys_exit_group kernel/exit.c:1163 [inline]
__se_sys_exit_group kernel/exit.c:1161 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1161
x64_sys_call+0x18bf/0x18c0 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f132ec60d05
Code: Unable to access opcode bytes at 0x7f132ec60cdb.
RSP: 002b:00007ffe413e3968 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f132ec60d05
RDX: 00000000000000e7 RSI: ffffffffffffffd8 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000009 R11: 0000000000000202 R12: 0000000000000000
R13: 00007f132ecfa118 R14: 00007f132ecfc3c8 R15: 00007f132ecfc3e0
</TASK>
=============================
[ BUG: Invalid wait context ]
syzkaller #0 Tainted: G W
-----------------------------
syz-executor363/5622 is trying to lock:
ffff888038241530 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
other info that might help us debug this:
context-{2:2}
locks held by syz-executor363/5622: 4, last CPU#0:
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#0: ffff88804093d380 (&sb->s_type->i_mutex_key#8/2){+.+.}-{4:4}, at: __simple_recursive_removal+0x19a/0x520 fs/libfs.c:619
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
#1: ffffffff8e53c398 (pin_fs_lock){+.+.}-{3:3}, at: simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
#2: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rtlock_slowlock_locked+0x2ab/0x3c20 kernel/locking/rtmutex.c:1874
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#3: ffff888038241b48 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1be/0x990 arch/x86/kvm/xen.c:1827
stack backtrace:
CPU: 0 UID: 0 PID: 5622 Comm: syz-executor363 Tainted: G W syzkaller #0 PREEMPT_{RT,(full)}
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_lock_invalid_wait_context kernel/locking/lockdep.c:4846 [inline]
check_wait_context kernel/locking/lockdep.c:4918 [inline]
__lock_acquire+0xef0/0x2e40 kernel/locking/lockdep.c:5204
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5906
rt_read_lock+0xcc/0x4b0 kernel/locking/spinlock_rt.c:249
kvm_xen_set_evtchn_fast+0x1f4/0x990 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x3a0/0xaf0 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x44a/0x900 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:rt_mutex_owner include/linux/rtmutex.h:52 [inline]
RIP: 0010:rtmutex_spin_on_owner kernel/locking/rtmutex.c:1504 [inline]
RIP: 0010:rtlock_slowlock_locked+0x34e5/0x3c20 kernel/locking/rtmutex.c:1893
Code: 80 3c 01 00 4c 8b b4 24 80 00 00 00 4c 8b 2c 24 74 08 4c 89 ef e8 db 0e df f6 48 8d 84 24 60 01 00 00 49 39 45 00 75 6c f3 90 <48> b8 00 00 00 00 00 fc ff df 48 8b 8c 24 a8 00 00 00 80 3c 01 00
RSP: 0018:ffffc90004e6f7a0 EFLAGS: 00000246
RAX: ffffc90004e6f900 RBX: 1ffff11006ff9bbe RCX: 1ffffffff1ca7871
RDX: 00000000e6b90d15 RSI: ffffffff8bcbd060 RDI: 0000000000000001
RBP: ffffc90004e6f9f0 R08: 1d00000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8e3c3880 R12: ffff888037fcddc0
R13: ffffffff8e53c388 R14: ffffffff8e53c390 R15: 1ffff11006ff9bba
rtlock_slowlock kernel/locking/rtmutex.c:1922 [inline]
rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
__rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
rt_spin_lock+0x165/0x400 kernel/locking/spinlock_rt.c:57
spin_lock include/linux/spinlock_rt.h:45 [inline]
simple_release_fs+0x2f/0xd0 fs/libfs.c:1120
__simple_recursive_removal+0x215/0x520 fs/libfs.c:623
debugfs_remove+0x5b/0x70 fs/debugfs/inode.c:781
kvm_destroy_vm_debugfs virt/kvm/kvm_main.c:988 [inline]
kvm_destroy_vm virt/kvm/kvm_main.c:1261 [inline]
kvm_put_kvm+0x147/0xae0 virt/kvm/kvm_main.c:1331
kvm_vm_release+0x46/0x50 virt/kvm/kvm_main.c:1354
__fput+0x42a/0xa80 fs/file_table.c:512
task_work_run+0x1d9/0x270 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x73a/0x2360 kernel/exit.c:1009
do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
__do_sys_exit_group kernel/exit.c:1163 [inline]
__se_sys_exit_group kernel/exit.c:1161 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1161
x64_sys_call+0x18bf/0x18c0 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f132ec60d05
Code: Unable to access opcode bytes at 0x7f132ec60cdb.
RSP: 002b:00007ffe413e3968 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f132ec60d05
RDX: 00000000000000e7 RSI: ffffffffffffffd8 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000009 R11: 0000000000000202 R12: 0000000000000000
R13: 00007f132ecfa118 R14: 00007f132ecfc3c8 R15: 00007f132ecfc3e0
</TASK>
----------------
Code disassembly (best guess):
0: 80 3c 01 00 cmpb $0x0,(%rcx,%rax,1)
4: 4c 8b b4 24 80 00 00 mov 0x80(%rsp),%r14
b: 00
c: 4c 8b 2c 24 mov (%rsp),%r13
10: 74 08 je 0x1a
12: 4c 89 ef mov %r13,%rdi
15: e8 db 0e df f6 call 0xf6df0ef5
1a: 48 8d 84 24 60 01 00 lea 0x160(%rsp),%rax
21: 00
22: 49 39 45 00 cmp %rax,0x0(%r13)
26: 75 6c jne 0x94
28: f3 90 pause
* 2a: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax <-- trapping instruction
31: fc ff df
34: 48 8b 8c 24 a8 00 00 mov 0xa8(%rsp),%rcx
3b: 00
3c: 80 3c 01 00 cmpb $0x0,(%rcx,%rax,1)
IsProbe: false
Reproduced: true
Console Output: [ 115.887758][ T33] kauditd_printk_skb: 10 callbacks suppressed
[ 115.887775][ T33] audit: type=1400 audit(1786541327.763:201): avc: denied { transition } for pid=5829 comm="sshd-session" path="/bin/sh" dev="sda1" ino=90 scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 115.905432][ T33] audit: type=1400 audit(1786541327.763:202): avc: denied { noatsecure } for pid=5829 comm="sshd-session" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 115.917204][ T33] audit: type=1400 audit(1786541327.763:203): avc: denied { rlimitinh } for pid=5829 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 115.928355][ T33] audit: type=1400 audit(1786541327.763:204): avc: denied { siginh } for pid=5829 comm="sh" scontext=system_u:system_r:sshd_t tcontext=root:sysadm_r:sysadm_t tclass=process permissive=1
[ 117.731131][ T33] audit: type=1400 audit(1786541329.603:205): avc: denied { write } for pid=5834 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 117.816274][ T33] audit: type=1400 audit(1786541329.693:206): avc: denied { write } for pid=5837 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 117.953117][ T33] audit: type=1400 audit(1786541329.823:207): avc: denied { write } for pid=5840 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 118.045447][ T33] audit: type=1400 audit(1786541329.923:208): avc: denied { write } for pid=5843 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.273939][ T33] audit: type=1400 audit(1786541332.143:209): avc: denied { write } for pid=5847 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.403671][ T33] audit: type=1400 audit(1786541332.273:210): avc: denied { write } for pid=5850 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 120.910529][ T33] kauditd_printk_skb: 2 callbacks suppressed
[ 120.910547][ T33] audit: type=1400 audit(1786541332.783:213): avc: denied { write } for pid=5859 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.003224][ T33] audit: type=1400 audit(1786541332.873:214): avc: denied { write } for pid=5862 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.396060][ T33] audit: type=1400 audit(1786541333.273:215): avc: denied { write } for pid=5867 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 121.570187][ T33] audit: type=1400 audit(1786541333.443:216): avc: denied { write } for pid=5870 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.157900][ T33] audit: type=1400 audit(1786541334.023:217): avc: denied { write } for pid=5877 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 122.243198][ T33] audit: type=1400 audit(1786541334.113:218): avc: denied { write } for pid=5880 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 123.158549][ T33] audit: type=1400 audit(1786541335.033:219): avc: denied { write } for pid=5887 comm="dhcpcd-run-hook" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
[ 123.241477][ T33] audit: type=1400 audit(1786541335.113:220): avc: denied { write } for pid=5890 comm="rm" name="hook-state" dev="tmpfs" ino=1794 scontext=system_u:system_r:dhcpc_t tcontext=system_u:object_r:tmpfs_t tclass=dir permissive=1
Warning: Permanently added '[localhost]:63790' (ED25519) to the list of known hosts.
[ 125.523473][ T33] audit: type=1400 audit(1786541337.393:221): avc: denied { read write } for pid=5901 comm="syz-executor877" name="kvm" dev="devtmpfs" ino=84 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:kvm_device_t tclass=chr_file permissive=1
[ 125.544929][ T33] audit: type=1400 audit(1786541337.413:222): avc: denied { open } for pid=5901 comm="syz-executor877" path="/dev/kvm" dev="devtmpfs" ino=84 scontext=root:sysadm_r:sysadm_t tcontext=system_u:object_r:kvm_device_t tclass=chr_file permissive=1
[ 126.538020][ C0]
[ 126.539160][ C0] =============================
[ 126.541225][ C0] [ BUG: Invalid wait context ]
[ 126.543376][ C0] syzkaller #1 Not tainted
[ 126.545415][ C0] -----------------------------
[ 126.548095][ C0] swapper/0/0 is trying to lock:
[ 126.551037][ C0] ffff88810d699bb0 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x9a0
[ 126.556554][ C0] other info that might help us debug this:
[ 126.560200][ C0] context-{2:2}
[ 126.562828][ C0] locks held by swapper/0/0: 1, last CPU#0:
[ 126.566268][ C0] #0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1bc/0x9a0
[ 126.571522][ C0] stack backtrace:
[ 126.573855][ C0] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #1 PREEMPT(full)
[ 126.573874][ C0] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 126.573883][ C0] Call Trace:
[ 126.573891][ C0] <IRQ>
[ 126.573912][ C0] dump_stack_lvl+0xe8/0x150
[ 126.573937][ C0] __lock_acquire+0xef0/0x2e50
[ 126.573957][ C0] ? __lock_acquire+0x6df/0x2e50
[ 126.573974][ C0] lock_acquire+0x115/0x350
[ 126.573988][ C0] ? kvm_xen_set_evtchn_fast+0x1f4/0x9a0
[ 126.574010][ C0] ? xa_load+0x1db/0x210
[ 126.574029][ C0] _raw_read_lock_irqsave+0x48/0x60
[ 126.574042][ C0] ? kvm_xen_set_evtchn_fast+0x1f4/0x9a0
[ 126.574058][ C0] kvm_xen_set_evtchn_fast+0x1f4/0x9a0
[ 126.574078][ C0] ? kvm_xen_set_evtchn_fast+0x1bc/0x9a0
[ 126.574097][ C0] xen_timer_callback+0x109/0x220
[ 126.574117][ C0] ? __pfx_xen_timer_callback+0x10/0x10
[ 126.574137][ C0] __hrtimer_run_queues+0x371/0xa10
[ 126.574163][ C0] hrtimer_interrupt+0x448/0x910
[ 126.574190][ C0] __sysvec_apic_timer_interrupt+0x102/0x430
[ 126.574211][ C0] sysvec_apic_timer_interrupt+0xa1/0xc0
[ 126.574226][ C0] </IRQ>
[ 126.574230][ C0] <TASK>
[ 126.574236][ C0] asm_sysvec_apic_timer_interrupt+0x1a/0x20
[ 126.574252][ C0] RIP: 0010:pv_native_safe_halt+0xf/0x20
[ 126.574268][ C0] Code: 8d 8f 02 e9 d3 03 03 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d b3 65 15 00 fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
[ 126.574280][ C0] RSP: 0018:ffffffff8e807ca0 EFLAGS: 00000246
[ 126.574293][ C0] RAX: 00000000001183f3 RBX: ffffffff819a214c RCX: 0000000080000001
[ 126.574304][ C0] RDX: 0000000000000001 RSI: ffffffff8e176c40 RDI: ffffffff8c326480
[ 126.574313][ C0] RBP: ffffffff8e807d78 R08: ffff8881386338db R09: 1ffff110270c671b
[ 126.574323][ C0] R10: dffffc0000000000 R11: ffffed10270c671c R12: 0000000000000000
[ 126.574332][ C0] R13: 1ffffffff1d11e20 R14: 1ffffffff1d00f9c R15: dffffc0000000000
[ 126.574396][ C0] ? do_idle+0x1cc/0x540
[ 126.574414][ C0] default_idle+0x9/0x20
[ 126.574430][ C0] default_idle_call+0x72/0xb0
[ 126.574446][ C0] do_idle+0x1cc/0x540
[ 126.574459][ C0] ? __pfx_do_idle+0x10/0x10
[ 126.574473][ C0] cpu_startup_entry+0x43/0x60
[ 126.574484][ C0] rest_init+0x378/0x3a0
[ 126.574502][ C0] ? __pfx_rest_init+0x10/0x10
[ 126.574521][ C0] ? __pfx_kernel_init+0x10/0x10
[ 126.574540][ C0] ? acpi_ut_status_exit+0x120/0x1f0
[ 126.574563][ C0] ? acpi_ut_status_exit+0x120/0x1f0
[ 126.574585][ C0] ? acpi_enable_subsystem+0x286/0x3c0
[ 126.574601][ C0] start_kernel+0x392/0x3e0
[ 126.574615][ C0] x86_64_start_reservations+0x24/0x30
[ 126.574635][ C0] x86_64_start_kernel+0x137/0x1b0
[ 126.574653][ C0] common_startup_64+0x13e/0x157
[ 126.574677][ C0] </TASK>
[+] open /dev/kvm successful.
[+] KVM_CREATE_VM successful.
[+] KVM_CREATE_VCPU successful.
[+] MY_KVM_XEN_VCPU_SET_ATTR successful.
[+] Waiting for timer to fire...
[+] Done.
[ 134.339652][ T1376] ieee802154 phy0 wpan0: encryption failed: -22
[ 134.342962][ T1376] ieee802154 phy1 wpan1: encryption failed: -22
Strace Output:
Crash Report: =============================
[ BUG: Invalid wait context ]
syzkaller #1 Not tainted
-----------------------------
swapper/0/0 is trying to lock:
ffff88810d699bb0 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x9a0 arch/x86/kvm/xen.c:1829
other info that might help us debug this:
context-{2:2}
locks held by swapper/0/0: 1, last CPU#0:
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1bc/0x9a0 arch/x86/kvm/xen.c:1827
stack backtrace:
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #1 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_lock_invalid_wait_context kernel/locking/lockdep.c:4846 [inline]
check_wait_context kernel/locking/lockdep.c:4918 [inline]
__lock_acquire+0xef0/0x2e50 kernel/locking/lockdep.c:5204
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5906
__raw_read_lock_irqsave include/linux/rwlock_api_smp.h:174 [inline]
_raw_read_lock_irqsave+0x48/0x60 kernel/locking/spinlock.c:240
kvm_xen_set_evtchn_fast+0x1f4/0x9a0 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x371/0xa10 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x448/0x910 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64
Code: 8d 8f 02 e9 d3 03 03 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d b3 65 15 00 fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
RSP: 0018:ffffffff8e807ca0 EFLAGS: 00000246
RAX: 00000000001183f3 RBX: ffffffff819a214c RCX: 0000000080000001
RDX: 0000000000000001 RSI: ffffffff8e176c40 RDI: ffffffff8c326480
RBP: ffffffff8e807d78 R08: ffff8881386338db R09: 1ffff110270c671b
R10: dffffc0000000000 R11: ffffed10270c671c R12: 0000000000000000
R13: 1ffffffff1d11e20 R14: 1ffffffff1d00f9c R15: dffffc0000000000
arch_safe_halt arch/x86/kernel/process.c:767 [inline]
default_idle+0x9/0x20 arch/x86/kernel/process.c:768
default_idle_call+0x72/0xb0 kernel/sched/idle.c:122
cpuidle_idle_call kernel/sched/idle.c:199 [inline]
do_idle+0x1cc/0x540 kernel/sched/idle.c:355
cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:454
rest_init+0x378/0x3a0 init/main.c:727
start_kernel+0x392/0x3e0 init/main.c:1185
x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291
common_startup_64+0x13e/0x157
</TASK>
----------------
Code disassembly (best guess):
0: 8d 8f 02 e9 d3 03 lea 0x3d3e902(%rdi),%ecx
6: 03 00 add (%rax),%eax
8: cc int3
9: cc int3
a: cc int3
b: 90 nop
c: 90 nop
d: 90 nop
e: 90 nop
f: 90 nop
10: 90 nop
11: 90 nop
12: 90 nop
13: 90 nop
14: 90 nop
15: 90 nop
16: 90 nop
17: 90 nop
18: 90 nop
19: 90 nop
1a: 90 nop
1b: f3 0f 1e fa endbr64
1f: 66 90 xchg %ax,%ax
21: 0f 00 2d b3 65 15 00 verw 0x1565b3(%rip) # 0x1565db
28: fb sti
29: f4 hlt
* 2a: c3 ret <-- trapping instruction
2b: cc int3
2c: cc int3
2d: cc int3
2e: cc int3
2f: cc int3
30: cc int3
31: cc int3
32: cc int3
33: cc int3
34: cc int3
35: cc int3
36: cc int3
37: cc int3
38: cc int3
39: cc int3
3a: cc int3
3b: 90 nop
3c: 90 nop
3d: 90 nop
3e: 90 nop
3f: 90 nop
|
| 118/4 |
2026/08/12 13:29 |
llm |
repro-oracle |
0m
Model:
Tokens:
input: 17169
output: 164
thoughts: 2449
Thoughts: **Summary of Debugging Thoughts**
I've been looking at a bug report concerning a crash in `kvm_xen_set_evtchn_fast`. Initially, the report mentioned "BUG: sleeping function called from invalid context" and "[ BUG: Invalid wait context ]", specifically in the context of a PREEMPT_RT kernel. This made sense because sleeping locks can't be used in interrupt contexts.
However, when I tried to reproduce the bug, I triggered the "[ BUG: Invalid wait context ]" on what appears to be a standard `PREEMPT(full)` kernel. This was a bit confusing at first. My thought process was to reconcile these observations.
I analyzed the stack traces provided. Both the original report and the reproducer show `kvm_xen_set_evtchn_fast` being called from `xen_timer_callback`. `xen_timer_callback` is an hrtimer callback, which runs in an interrupt (hardirq) context. Inside `kvm_xen_set_evtchn_fast`, there's an attempt to acquire a lock, `gpc->lock`.
The core of the issue, as I see it, lies in how locks behave in different kernel configurations. In a PREEMPT_RT kernel, a `rwlock_t` (which `gpc->lock` appears to be) is a sleeping lock. Taking a sleeping lock in an interrupt context is fundamentally forbidden and leads to the "sleeping function called from invalid context" error.
In a non-RT kernel, even a `PREEMPT(full)` one, `rwlock_t` typically behaves more like a spinlock. While taking a spinlock in an interrupt context is generally fine *if* it's an IRQ-safe spinlock, the `[ BUG: Invalid wait context ]` from lockdep suggests that this particular lock acquisition is still problematic. Lockdep is designed to catch situations where a lock is acquired in a context that is "more atomic" than the lock's inherent "wait context."
The stack traces clearly show `kvm_xen_set_evtchn_fast` is invoked from `xen_timer_callback` (hardirq context), and within it, a read lock (`_raw_read_lock_irqsave` or `rt_read_lock`) is attempted on `gpc->lock`. This pattern is identical in both reports. The crucial insight is that even on a non-RT kernel, lockdep is flagging this as an invalid wait context. This implies that `gpc->lock` or the way it's being acquired within the hardirq context of `xen_timer_callback` violates lockdep's rules, regardless of whether the lock itself would *sleep* or not.
Therefore, I'm confident that the bug is indeed the same across both scenarios: an attempt to acquire `gpc->lock` from within a hardirq context via `kvm_xen_set_evtchn_fast`, originating from `xen_timer_callback`. The specific error message ("sleeping function..." vs. "invalid wait context") is a consequence of the kernel's PREEMPT configuration, but the underlying concurrency violation is consistent. I will mark `TitleMatches` as true.
|
| 119/4 |
2026/08/12 13:29 |
tool |
set-results |
0m
Args: map[Feedback:The reproducer successfully triggered the target bug. The crash report shows `[ BUG: Invalid wait context ]` with the exact same stack trace as the original report: `xen_timer_callback` -> `kvm_xen_set_evtchn_fast` -> lock acquisition. The original report was on a PREEMPT_RT kernel, which additionally triggered a "sleeping function called from invalid context" warning because spinlocks/rwlocks sleep in RT, but the underlying issue (taking `gpc->lock` in hardirq context from the hrtimer callback) is identical and caught by lockdep's wait context checks in both cases. ProbePassed:false TerminalError: TitleMatches:true]
Results: map[Feedback:The reproducer successfully triggered the target bug. The crash report shows `[ BUG: Invalid wait context ]` with the exact same stack trace as the original report: `xen_timer_callback` -> `kvm_xen_set_evtchn_fast` -> lock acquisition. The original report was on a PREEMPT_RT kernel, which additionally triggered a "sleeping function called from invalid context" warning because spinlocks/rwlocks sleep in RT, but the underlying issue (taking `gpc->lock` in hardirq context from the hrtimer callback) is identical and caught by lockdep's wait context checks in both cases. ProbePassed:false TerminalError: TitleMatches:true]
|
| 120/3 |
2026/08/12 13:29 |
action |
loop-controller |
0m
Results: map[CapabilitiesVerified:true ContinueSignal: EquivalenceAnalysis:The reproducer successfully triggered the target bug. The crash report shows `[ BUG: Invalid wait context ]` with the exact same stack trace as the original report: `xen_timer_callback` -> `kvm_xen_set_evtchn_fast` -> lock acquisition. The original report was on a PREEMPT_RT kernel, which additionally triggered a "sleeping function called from invalid context" warning because spinlocks/rwlocks sleep in RT, but the underlying issue (taking `gpc->lock` in hardirq context from the hrtimer callback) is identical and caught by lockdep's wait context checks in both cases. OracleFeedback:The reproducer successfully triggered the target bug. The crash report shows `[ BUG: Invalid wait context ]` with the exact same stack trace as the original report: `xen_timer_callback` -> `kvm_xen_set_evtchn_fast` -> lock acquisition. The original report was on a PREEMPT_RT kernel, which additionally triggered a "sleeping function called from invalid context" warning because spinlocks/rwlocks sleep in RT, but the underlying issue (taking `gpc->lock` in hardirq context from the hrtimer callback) is identical and caught by lockdep's wait context checks in both cases. ReproC:#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/kvm.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#define KVM_XEN_VCPU_ATTR_TYPE_TIMER 0x7
#define KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL ((uint32_t)(-1))
struct my_kvm_xen_vcpu_attr {
uint16_t type;
uint16_t pad[3];
union {
uint64_t gpa;
uint64_t hva;
uint64_t pad[8];
struct {
uint64_t state;
uint64_t state_entry_time;
uint64_t time_running;
uint64_t time_runnable;
uint64_t time_blocked;
uint64_t time_offline;
} runstate;
uint32_t vcpu_id;
struct {
uint32_t port;
uint32_t priority;
uint64_t expires_ns;
} timer;
uint8_t vector;
} u;
};
#define MY_KVM_XEN_VCPU_SET_ATTR _IOW(KVMIO, 0xcb, struct my_kvm_xen_vcpu_attr)
int main(void)
{
int kvm_fd, vm_fd, vcpu_fd;
struct my_kvm_xen_vcpu_attr attr;
int res;
kvm_fd = open("/dev/kvm", O_RDWR);
if (kvm_fd < 0) {
printf("[-] Failed to open /dev/kvm: %s\n", strerror(errno));
exit(1);
}
printf("[+] open /dev/kvm successful.\n");
vm_fd = ioctl(kvm_fd, KVM_CREATE_VM, 0);
if (vm_fd < 0) {
printf("[-] Failed to KVM_CREATE_VM: %s\n", strerror(errno));
exit(1);
}
printf("[+] KVM_CREATE_VM successful.\n");
vcpu_fd = ioctl(vm_fd, KVM_CREATE_VCPU, 0);
if (vcpu_fd < 0) {
printf("[-] Failed to KVM_CREATE_VCPU: %s\n", strerror(errno));
exit(1);
}
printf("[+] KVM_CREATE_VCPU successful.\n");
memset(&attr, 0, sizeof(attr));
attr.type = KVM_XEN_VCPU_ATTR_TYPE_TIMER;
attr.u.timer.port = 1;
attr.u.timer.priority = KVM_IRQ_ROUTING_XEN_EVTCHN_PRIO_2LEVEL;
attr.u.timer.expires_ns = 1000000000ULL;
res = ioctl(vcpu_fd, MY_KVM_XEN_VCPU_SET_ATTR, &attr);
if (res < 0) {
printf("[-] Failed to MY_KVM_XEN_VCPU_SET_ATTR: %s\n", strerror(errno));
exit(1);
}
printf("[+] MY_KVM_XEN_VCPU_SET_ATTR successful.\n");
printf("[+] Waiting for timer to fire...\n");
sleep(2);
close(vcpu_fd);
close(vm_fd);
close(kvm_fd);
printf("[+] Done.\n");
return 0;
}
Reproduced:true ReproducedBugTitle:WARNING: locking bug in kvm_xen_set_evtchn_fast ReproducedCrashReport:=============================
[ BUG: Invalid wait context ]
syzkaller #1 Not tainted
-----------------------------
swapper/0/0 is trying to lock:
ffff88810d699bb0 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x9a0 arch/x86/kvm/xen.c:1829
other info that might help us debug this:
context-{2:2}
locks held by swapper/0/0: 1, last CPU#0:
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline]
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline]
#0: ffff88810d69a110 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1bc/0x9a0 arch/x86/kvm/xen.c:1827
stack backtrace:
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #1 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<IRQ>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_lock_invalid_wait_context kernel/locking/lockdep.c:4846 [inline]
check_wait_context kernel/locking/lockdep.c:4918 [inline]
__lock_acquire+0xef0/0x2e50 kernel/locking/lockdep.c:5204
lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5906
__raw_read_lock_irqsave include/linux/rwlock_api_smp.h:174 [inline]
_raw_read_lock_irqsave+0x48/0x60 kernel/locking/spinlock.c:240
kvm_xen_set_evtchn_fast+0x1f4/0x9a0 arch/x86/kvm/xen.c:1829
xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:141
__run_hrtimer kernel/time/hrtimer.c:2065 [inline]
__hrtimer_run_queues+0x371/0xa10 kernel/time/hrtimer.c:2122
hrtimer_interrupt+0x448/0x910 kernel/time/hrtimer.c:2241
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline]
__sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64
Code: 8d 8f 02 e9 d3 03 03 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d b3 65 15 00 fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
RSP: 0018:ffffffff8e807ca0 EFLAGS: 00000246
RAX: 00000000001183f3 RBX: ffffffff819a214c RCX: 0000000080000001
RDX: 0000000000000001 RSI: ffffffff8e176c40 RDI: ffffffff8c326480
RBP: ffffffff8e807d78 R08: ffff8881386338db R09: 1ffff110270c671b
R10: dffffc0000000000 R11: ffffed10270c671c R12: 0000000000000000
R13: 1ffffffff1d11e20 R14: 1ffffffff1d00f9c R15: dffffc0000000000
arch_safe_halt arch/x86/kernel/process.c:767 [inline]
default_idle+0x9/0x20 arch/x86/kernel/process.c:768
default_idle_call+0x72/0xb0 kernel/sched/idle.c:122
cpuidle_idle_call kernel/sched/idle.c:199 [inline]
do_idle+0x1cc/0x540 kernel/sched/idle.c:355
cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:454
rest_init+0x378/0x3a0 init/main.c:727
start_kernel+0x392/0x3e0 init/main.c:1185
x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291
common_startup_64+0x13e/0x157
</TASK>
----------------
Code disassembly (best guess):
0: 8d 8f 02 e9 d3 03 lea 0x3d3e902(%rdi),%ecx
6: 03 00 add (%rax),%eax
8: cc int3
9: cc int3
a: cc int3
b: 90 nop
c: 90 nop
d: 90 nop
e: 90 nop
f: 90 nop
10: 90 nop
11: 90 nop
12: 90 nop
13: 90 nop
14: 90 nop
15: 90 nop
16: 90 nop
17: 90 nop
18: 90 nop
19: 90 nop
1a: 90 nop
1b: f3 0f 1e fa endbr64
1f: 66 90 xchg %ax,%ax
21: 0f 00 2d b3 65 15 00 verw 0x1565b3(%rip) # 0x1565db
28: fb sti
29: f4 hlt
* 2a: c3 ret <-- trapping instruction
2b: cc int3
2c: cc int3
2d: cc int3
2e: cc int3
2f: cc int3
30: cc int3
31: cc int3
32: cc int3
33: cc int3
34: cc int3
35: cc int3
36: cc int3
37: cc int3
38: cc int3
39: cc int3
3a: cc int3
3b: 90 nop
3c: 90 nop
3d: 90 nop
3e: 90 nop
3f: 90 nop
]
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