------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: lib/refcount.c:28 at refcount_warn_saturate+0xb2/0x110 lib/refcount.c:28, CPU#1: syz.4.13944/23686
Modules linked in:
CPU: 1 UID: 0 PID: 23686 Comm: syz.4.13944 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:refcount_warn_saturate+0xb2/0x110 lib/refcount.c:28
Code: 74 c3 8f 0b 67 48 0f b9 3a eb 4a e8 b8 5a f3 fc 48 8d 3d 71 c3 8f 0b 67 48 0f b9 3a eb 37 e8 a5 5a f3 fc 48 8d 3d 6e c3 8f 0b <67> 48 0f b9 3a eb 24 e8 92 5a f3 fc 48 8d 3d 6b c3 8f 0b 67 48 0f
RSP: 0000:ffffc90000a08c68 EFLAGS: 00010246
RAX: ffffffff84d316db RBX: 0000000000000003 RCX: ffff888027a79f00
RDX: 0000000000000100 RSI: ffffffff8f364dc0 RDI: ffffffff9062da50
RBP: ffffc90000a08d70 R08: ffff888027a79f00 R09: 0000000000000005
R10: 0000000000000004 R11: 0000000000000100 R12: 0000000000000001
R13: 0000000100043eef R14: ffff888052da0020 R15: ffff888052da01b8
FS: 0000000000000000(0000) GS:ffff888125055000(0000) knlGS:0000000000000000
CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000080118018 CR3: 0000000043b9c000 CR4: 00000000003526f0
Call Trace:
call_timer_fn+0x192/0x5e0 kernel/time/timer.c:1748
expire_timers kernel/time/timer.c:1799 [inline]
__run_timers kernel/time/timer.c:2374 [inline]
__run_timer_base+0x652/0x8b0 kernel/time/timer.c:2386
run_timer_base kernel/time/timer.c:2395 [inline]
run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2405
handle_softirqs+0x225/0x840 kernel/softirq.c:622
__do_softirq kernel/softirq.c:656 [inline]
invoke_softirq kernel/softirq.c:496 [inline]
__irq_exit_rcu+0xca/0x220 kernel/softirq.c:735
irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1062
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:debug_check_no_obj_freed+0x433/0x450 lib/debugobjects.c:1202
Code: 35 aa 48 71 09 b9 0a 00 00 00 bf 08 00 00 00 48 c7 c2 40 b4 36 8f e8 8c fb ae fc 65 48 8b 05 94 59 8e 0e 48 3b 44 24 70 75 14 <48> 83 c4 78 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc e8 44
RSP: 0000:ffffc900044977e0 EFLAGS: 00000246
RAX: c66781f04a718f00 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8e22b35b RDI: 00000000ffffffff
RBP: 0000000000a1a008 R08: ffffffff905783f7 R09: 1ffffffff20af07e
R10: dffffc0000000000 R11: fffffbfff20af07f R12: 0000000000000000
R13: ffff888026297000 R14: 0000000000000000 R15: 0000000000000000
slab_free_hook mm/slub.c:2636 [inline]
slab_free mm/slub.c:6405 [inline]
kfree+0x13e/0x640 mm/slub.c:6720
kvm_io_bus_destroy virt/kvm/kvm_main.c:5792 [inline]
kvm_destroy_vm virt/kvm/kvm_main.c:1272 [inline]
kvm_put_kvm+0x5d0/0xae0 virt/kvm/kvm_main.c:1331
kvm_vm_release+0x43/0x50 virt/kvm/kvm_main.c:1354
__fput+0x418/0xa50 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
get_signal+0x121b/0x12c0 kernel/signal.c:3046
arch_do_signal_or_restart+0xbb/0x860 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
exit_to_user_mode_loop+0x104/0x730 kernel/entry/common.c:101
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
__do_fast_syscall_32+0x45b/0x6f0 arch/x86/entry/syscall_32.c:310
do_fast_syscall_32+0x33/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf700f0ec
Code: Unable to access opcode bytes at 0xf700f0c2.
RSP: 002b:00000000f53fd50c EFLAGS: 00000206 ORIG_RAX: 0000000000000127
RAX: fffffffffffffffc RBX: 00000000ffffff9c RCX: 0000000080004280
RDX: 0000000000000000 RSI: 000000000000002c RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
----------------
Code disassembly (best guess), 3 bytes skipped:
0: 0b 67 48 or 0x48(%rdi),%esp
3: 0f b9 3a ud1 (%rdx),%edi
6: eb 4a jmp 0x52
8: e8 b8 5a f3 fc call 0xfcf35ac5
d: 48 8d 3d 71 c3 8f 0b lea 0xb8fc371(%rip),%rdi # 0xb8fc385
14: 67 48 0f b9 3a ud1 (%edx),%rdi
19: eb 37 jmp 0x52
1b: e8 a5 5a f3 fc call 0xfcf35ac5
20: 48 8d 3d 6e c3 8f 0b lea 0xb8fc36e(%rip),%rdi # 0xb8fc395
* 27: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2c: eb 24 jmp 0x52
2e: e8 92 5a f3 fc call 0xfcf35ac5
33: 48 8d 3d 6b c3 8f 0b lea 0xb8fc36b(%rip),%rdi # 0xb8fc3a5
3a: 67 addr32
3b: 48 rex.W
3c: 0f .byte 0xf