syzbot

 sign-in | mailing list | source | docs
🐞 Open [717]
🐞 Fixed [181]
🐞 Invalid [640]
≡ Crashes
Kernel Health Bugs/Month Bug Lifetimes Fuzzing
💬 Send us feedback

INFO: rcu detected stall in kvm_vcpu_ioctl

Status: upstream: reported C repro on 2019/11/13 08:08
Reported-by: syzbot+10980f8ef2d3d723c7a5@syzkaller.appspotmail.com
First crash: 2376d, last: 2218d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Similar bugs (6)
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 646d 646d 0/29 auto-obsoleted due to no activity on 2024/11/06 13:35
upstream INFO: rcu detected stall in kvm_vcpu_ioctl (4) kvm kvm-x86 1 C error 4 35d 140d 0/29 upstream: reported C repro on 2025/12/27 03:34
upstream INFO: rcu detected stall in kvm_vcpu_ioctl (3) kvm-x86 1 2 441d 506d 0/29 auto-obsoleted due to no activity on 2025/05/30 15:19
upstream INFO: rcu detected stall in kvm_vcpu_ioctl mm 1 C error unreliable 251 1627d 2804d 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 1662d 2317d 0/1 upstream: reported C repro on 2020/01/10 19:56
linux-5.15 INFO: rcu detected stall in kvm_vcpu_ioctl origin:lts-only 1 C error 9 90d 344d 0/3 upstream: reported C repro on 2025/06/05 19:21
▶ ▼ Last patch testing requests (4)
Created Duration User Patch Repo Result
2022/12/11 03:31 13m retest repro linux-4.14.y report log
2022/12/10 17:31 10m retest repro linux-4.14.y report log
2022/08/28 14:27 12m retest repro linux-4.14.y error
2022/08/28 13:27 10m retest repro linux-4.14.y report log
▶ ▼ Fix bisection attempts (3)
Created Duration User Patch Repo Result
2020/02/17 00:54 19m bisect fix linux-4.14.y error job log
2020/01/18 00:17 37m bisect fix linux-4.14.y OK (0) job log log
2019/12/18 23:40 36m bisect fix linux-4.14.y OK (0) job log log

Sample crash report:
INFO: rcu_preempt detected stalls on CPUs/tasks:
	(detected by 1, t=10502 jiffies, g=3746, c=3745, q=13)
All QSes seen, last rcu_preempt kthread activity 10502 (4295093353-4295082851), jiffies_till_next_fqs=1, root ->qsmask 0x0
syz-executor421 R  running task    28176  9059   7455 0x00000800
Call Trace:
 <IRQ>
 sched_show_task kernel/sched/core.c:5168 [inline]
 sched_show_task.cold+0x2e3/0x347 kernel/sched/core.c:5143
 print_other_cpu_stall kernel/rcu/tree.c:1501 [inline]
 check_cpu_stall kernel/rcu/tree.c:1616 [inline]
 __rcu_pending kernel/rcu/tree.c:3390 [inline]
 rcu_pending kernel/rcu/tree.c:3452 [inline]
 rcu_check_callbacks.cold+0xd3f/0xdaa kernel/rcu/tree.c:2792
 update_process_times+0x29/0x60 kernel/time/timer.c:1590
 tick_sched_handle+0x7d/0x150 kernel/time/tick-sched.c:165
 tick_sched_timer+0x3e/0x120 kernel/time/tick-sched.c:1223
 __run_hrtimer kernel/time/hrtimer.c:1223 [inline]
 __hrtimer_run_queues+0x25c/0xbb0 kernel/time/hrtimer.c:1287
 hrtimer_interrupt+0x1e6/0x5e0 kernel/time/hrtimer.c:1321
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1075 [inline]
 smp_apic_timer_interrupt+0x117/0x5e0 arch/x86/kernel/apic/apic.c:1100
 apic_timer_interrupt+0x8f/0xa0 arch/x86/entry/entry_64.S:792
 </IRQ>
RIP: 0010:vcpu_enter_guest+0xd66/0x5240 arch/x86/kvm/x86.c:7297
RSP: 0018:ffff888080e0fae0 EFLAGS: 00000297 ORIG_RAX: ffffffffffffff10
RAX: ffff8880a6dba6c0 RBX: ffff8880a6dba6c0 RCX: 1ffff11014db75ec
RDX: 0000000000000000 RSI: ffff8880a6dbaf40 RDI: ffff8880a6dbaf3c
RBP: ffff888080e0fbe0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880a8ae85c0
R13: ffff8880a8ae86a0 R14: ffff8880a8ae85e8 R15: fffffcf1740d116c
 vcpu_run arch/x86/kvm/x86.c:7379 [inline]
 kvm_arch_vcpu_ioctl_run+0x2fe/0xfd0 arch/x86/kvm/x86.c:7546
 kvm_vcpu_ioctl+0x3df/0xc70 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2661
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x75a/0xfe0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x44cb49
RSP: 002b:00007f86562d7ce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006e8a08 RCX: 000000000044cb49
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000006
RBP: 00000000006e8a00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006e8a0c
R13: 00007ffd83b0303f R14: 00007f86562d89c0 R15: 20c49ba5e353f7cf
rcu_preempt kthread starved for 10502 jiffies! g3746 c3745 f0x2 RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=0
rcu_preempt     R  running task    29920     8      2 0x80000000
Call Trace:
 schedule+0x8d/0x1b0 kernel/sched/core.c:3428
 schedule_timeout+0x43c/0xe40 kernel/time/timer.c:1746
 rcu_gp_kthread+0xb8e/0x1ce0 kernel/rcu/tree.c:2255
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Crashes (12):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/03/07 21:22 linux-4.14.y 78d697fc93f9 2e9971bb .config console log report syz C ci2-linux-4-14
2019/11/13 07:07 linux-4.14.y 4762bcd451a9 048f2d49 .config console log report syz ci2-linux-4-14
2020/04/18 19:05 linux-4.14.y c10b57a567e4 365fba24 .config console log report ci2-linux-4-14
2020/03/22 19:15 linux-4.14.y 01364dad1d45 78267cec .config console log report ci2-linux-4-14
2020/03/22 18:56 linux-4.14.y 01364dad1d45 78267cec .config console log report ci2-linux-4-14
2020/03/16 09:23 linux-4.14.y 12cd844a39ed 749688d2 .config console log report ci2-linux-4-14
2020/03/10 13:42 linux-4.14.y 78d697fc93f9 35f53e45 .config console log report ci2-linux-4-14
2020/03/10 06:08 linux-4.14.y 78d697fc93f9 35f53e45 .config console log report ci2-linux-4-14
2020/03/09 04:57 linux-4.14.y 78d697fc93f9 2e9971bb .config console log report ci2-linux-4-14
2020/03/02 07:46 linux-4.14.y 78d697fc93f9 4a4e0509 .config console log report ci2-linux-4-14
2020/03/01 16:22 linux-4.14.y 78d697fc93f9 c88c7b75 .config console log report ci2-linux-4-14
2019/11/14 17:04 linux-4.14.y 775d01b65b5d 048f2d49 .config console log report ci2-linux-4-14
* Struck through repros no longer work on HEAD.