syzbot

 sign-in | mailing list | source | docs
🐞 Open [1470]
≡ Subsystems
🐞 Fixed [6785]
🐞 Invalid [17509]
⬇ Missing Backports [220]
≡ Crashes
Kernel Health Bugs/Month Bug Lifetimes Fuzzing
Total Repo Heatmap Subsystems Heatmap
💬 Send us feedback

INFO: rcu detected stall in kvm_vcpu_ioctl (3)

Status: auto-obsoleted due to no activity on 2025/05/30 15:19
Subsystems: kvm-x86
[Documentation on labels]
First crash: 348d, last: 282d
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in kvm_vcpu_ioctl (2) kvm-x86 1 1 488d 488d 0/29 auto-obsoleted due to no activity on 2024/11/06 13:35
upstream INFO: rcu detected stall in kvm_vcpu_ioctl mm 1 C error unreliable 251 1469d 2646d 0/29 closed as invalid on 2022/02/08 10:48
linux-4.19 INFO: rcu detected stall in kvm_vcpu_ioctl 1 C error 46 1503d 2159d 0/1 upstream: reported C repro on 2020/01/10 19:56
linux-4.14 INFO: rcu detected stall in kvm_vcpu_ioctl 1 C error 12 2060d 2218d 0/1 upstream: reported C repro on 2019/11/13 08:08
linux-5.15 INFO: rcu detected stall in kvm_vcpu_ioctl 1 5 12d 186d 0/3 upstream: reported on 2025/06/05 19:21
linux-4.19 BUG: soft lockup in kvm_vcpu_ioctl 1 C error 2 1682d 1685d 0/1 upstream: reported C repro on 2021/04/28 21:34
android-5-15 BUG: soft lockup in kvm_vcpu_ioctl 1 1 604d 604d 0/2 auto-obsoleted due to no activity on 2024/07/12 20:15

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (1 GPs behind) idle=3454/1/0x4000000000000000 softirq=118104/118105 fqs=1
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P18240/1:b..l
rcu: 	(detected by 1, t=10505 jiffies, g=120549, q=395 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 18239 Comm: syz.7.3364 Not tainted 6.14.0-rc4-syzkaller-00242-g7a5668899f54 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:__lock_acquire+0xe8/0x3c40 kernel/locking/lockdep.c:5091
Code: 85 15 14 00 00 44 8b 0d 8a 29 cc 0e 45 85 c9 0f 84 b4 0e 00 00 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 80 3c 02 00 <0f> 85 96 2c 00 00 49 8b 04 24 48 3d a0 27 83 93 0f 84 89 0e 00 00
RSP: 0018:ffffc90000007be8 EFLAGS: 00000046
RAX: dffffc0000000000 RBX: 0000000000000001 RCX: 0000000000000000
RDX: 1ffff110170c58d3 RSI: 1ffff92000000f8f RDI: ffff8880b862c698
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff90625817 R11: 0000000000000002 R12: ffff8880b862c698
R13: ffff88805ebf2440 R14: 0000000000000000 R15: 0000000000000000
FS:  00007f97f70106c0(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000060009178 CR3: 000000005c85c000 CR4: 00000000003526f0
Call Trace:
 <NMI>
 </NMI>
 <IRQ>
 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5851
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
 _raw_spin_lock_irq+0x36/0x50 kernel/locking/spinlock.c:170
 __run_hrtimer kernel/time/hrtimer.c:1805 [inline]
 __hrtimer_run_queues+0x2be/0xae0 kernel/time/hrtimer.c:1865
 hrtimer_interrupt+0x392/0x8e0 kernel/time/hrtimer.c:1927
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1038 [inline]
 __sysvec_apic_timer_interrupt+0x10f/0x400 arch/x86/kernel/apic/apic.c:1055
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
 sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1049
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:__vmcs_writel arch/x86/kvm/vmx/vmx_ops.h:225 [inline]
RIP: 0010:vmcs_write16 arch/x86/kvm/vmx/vmx_ops.h:234 [inline]
RIP: 0010:__vmx_set_segment+0x390/0x9f0 arch/x86/kvm/vmx/vmx.c:3636
Code: 8b 48 89 fa 48 c1 ea 03 0f b6 04 02 84 c0 74 08 3c 03 0f 8e 3a 05 00 00 48 89 e8 48 c1 e0 04 44 8b b8 e0 df 64 8b 45 0f 79 fe <2e> 0f 86 93 03 00 00 e8 64 6b 69 00 48 8d 7b 0e 48 b8 00 00 00 00
RSP: 0018:ffffc9000d47f7d0 EFLAGS: 00000202
RAX: 0000000000000050 RBX: ffffc9000d47f858 RCX: ffffc9000c271000
RDX: 1ffffffff16c9c06 RSI: ffffffff815075cc RDI: ffffffff8b64e030
RBP: 0000000000000005 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff88807be50000
R13: 0000000000000005 R14: 0000000000000058 R15: 000000000000080a
 load_vmcs12_host_state+0xe3e/0x1850 arch/x86/kvm/vmx/nested.c:4776
 nested_vmx_enter_non_root_mode+0x371c/0x46a0 arch/x86/kvm/vmx/nested.c:3647
 nested_vmx_run+0x4fc/0x1150 arch/x86/kvm/vmx/nested.c:3738
 __vmx_handle_exit arch/x86/kvm/vmx/vmx.c:6629 [inline]
 vmx_handle_exit+0x6a4/0x1a30 arch/x86/kvm/vmx/vmx.c:6646
 vcpu_enter_guest arch/x86/kvm/x86.c:11092 [inline]
 vcpu_run+0x3032/0x4f50 arch/x86/kvm/x86.c:11253
 kvm_arch_vcpu_ioctl_run+0x865/0x17f0 arch/x86/kvm/x86.c:11575
 kvm_vcpu_ioctl+0x5ea/0x16b0 virt/kvm/kvm_main.c:4378
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl fs/ioctl.c:892 [inline]
 __x64_sys_ioctl+0x190/0x200 fs/ioctl.c:892
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f97f618d169
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f97f7010038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f97f63a5fa0 RCX: 00007f97f618d169
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 000000000000000a
RBP: 00007f97f620e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f97f63a5fa0 R15: 00007fff5cd50f38
 </TASK>
task:syz.8.3363      state:R  running task     stack:25952 pid:18240 tgid:18237 ppid:12923  task_flags:0x400140 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5378 [inline]
 __schedule+0xf43/0x5890 kernel/sched/core.c:6765
 preempt_schedule_common+0x44/0xc0 kernel/sched/core.c:6944
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk.S:12
 __raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_unlock+0x3e/0x50 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 finish_fault+0x9e7/0x1010 mm/memory.c:5273
 do_read_fault mm/memory.c:5407 [inline]
 do_fault mm/memory.c:5537 [inline]
 do_pte_missing+0xef8/0x3e10 mm/memory.c:4058
 handle_pte_fault mm/memory.c:5900 [inline]
 __handle_mm_fault+0x1166/0x2c60 mm/memory.c:6043
 handle_mm_fault+0x3fa/0xaa0 mm/memory.c:6212
 faultin_page mm/gup.c:1196 [inline]
 __get_user_pages+0x773/0x36f0 mm/gup.c:1491
 populate_vma_page_range+0x27f/0x3a0 mm/gup.c:1929
 __mm_populate+0x1d6/0x380 mm/gup.c:2032
 mm_populate include/linux/mm.h:3386 [inline]
 vm_mmap_pgoff+0x2d3/0x3a0 mm/util.c:580
 ksys_mmap_pgoff+0x7d/0x5c0 mm/mmap.c:607
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:89 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:82 [inline]
 __x64_sys_mmap+0x125/0x190 arch/x86/kernel/sys_x86_64.c:82
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fae07d8d169
RSP: 002b:00007fae08b46038 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007fae07fa5fa0 RCX: 00007fae07d8d169
RDX: b635773f06ebbeee RSI: 0000000000b36000 RDI: 0000400000000000
RBP: 00007fae07e0e2a0 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000008031 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fae07fa5fa0 R15: 00007ffd9d9b4368
 </TASK>
rcu: rcu_preempt kthread starved for 10500 jiffies! g120549 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:28064 pid:17    tgid:17    ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5378 [inline]
 __schedule+0xf43/0x5890 kernel/sched/core.c:6765
 __schedule_loop kernel/sched/core.c:6842 [inline]
 schedule+0xe7/0x350 kernel/sched/core.c:6857
 schedule_timeout+0x124/0x280 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1eb/0xb00 kernel/rcu/tree.c:2024
 rcu_gp_kthread+0x271/0x380 kernel/rcu/tree.c:2226
 kthread+0x3af/0x750 kernel/kthread.c:464
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 UID: 0 PID: 17862 Comm: kworker/u8:26 Not tainted 6.14.0-rc4-syzkaller-00242-g7a5668899f54 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:write_comp_data+0x42/0x90 kernel/kcov.c:246
Code: a9 00 01 ff 00 74 1d f6 c4 01 74 67 a9 00 00 0f 00 75 60 a9 00 00 f0 00 75 59 8b 82 2c 16 00 00 85 c0 74 4f 8b 82 08 16 00 00 <83> f8 03 75 44 48 8b 82 10 16 00 00 8b 92 0c 16 00 00 48 8b 38 48
RSP: 0018:ffffc900111b7920 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff8880b8646a00 RCX: ffffffff81add35a
RDX: ffff888048468000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000006 R12: ffffed10170c8d41
R13: 0000000000000001 R14: ffff8880b873fe80 R15: ffff8880b8646a08
FS:  0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9233ed56c0 CR3: 000000000df80000 CR4: 00000000003526f0
DR0: 0000000440000000 DR1: 0000000000000008 DR2: 000000000000007f
DR3: ffff7ffffffffffd DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 </IRQ>
 <TASK>
 csd_lock_wait kernel/smp.c:340 [inline]
 smp_call_function_many_cond+0x4ea/0x12c0 kernel/smp.c:885
 on_each_cpu_cond_mask+0x40/0x90 kernel/smp.c:1052
 on_each_cpu include/linux/smp.h:71 [inline]
 text_poke_sync arch/x86/kernel/alternative.c:2118 [inline]
 text_poke_bp_batch+0x22b/0x760 arch/x86/kernel/alternative.c:2328
 text_poke_flush arch/x86/kernel/alternative.c:2519 [inline]
 text_poke_flush arch/x86/kernel/alternative.c:2516 [inline]
 text_poke_finish+0x30/0x40 arch/x86/kernel/alternative.c:2526
 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
 jump_label_update+0x1d7/0x400 kernel/jump_label.c:920
 static_key_enable_cpuslocked+0x1b7/0x270 kernel/jump_label.c:210
 static_key_enable+0x1a/0x20 kernel/jump_label.c:223
 toggle_allocation_gate mm/kfence/core.c:850 [inline]
 toggle_allocation_gate+0xfc/0x260 mm/kfence/core.c:842
 process_one_work+0x9c5/0x1ba0 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3319 [inline]
 worker_thread+0x6c8/0xf00 kernel/workqueue.c:3400
 kthread+0x3af/0x750 kernel/kthread.c:464
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/03/01 15:15 upstream 7a5668899f54 1e7a43e1 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in kvm_vcpu_ioctl
2024/12/26 09:34 upstream 9b2ffa6148b1 444551c4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in kvm_vcpu_ioctl
* Struck through repros no longer work on HEAD.