syzbot


INFO: rcu detected stall in kvm_dev_ioctl (2)

Status: upstream: reported on 2026/01/10 12:35
Reported-by: syzbot+45d460eb4e2a719dfe68@syzkaller.appspotmail.com
First crash: 3d13h, last: 3d13h
Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in kvm_dev_ioctl 1 1 569d 569d 0/3 auto-obsoleted due to no activity on 2024/10/01 03:25
upstream INFO: rcu detected stall in kvm_dev_ioctl (2) mm 1 1 2198d 2198d 0/29 closed as invalid on 2020/01/08 05:23
linux-6.6 INFO: rcu detected stall in kvm_dev_ioctl 1 1 156d 156d 0/2 auto-obsoleted due to no activity on 2025/11/18 13:11
upstream INFO: rcu detected stall in kvm_dev_ioctl (5) mm 1 9 334d 624d 0/29 auto-obsoleted due to no activity on 2025/05/14 19:07
upstream INFO: rcu detected stall in kvm_dev_ioctl (4) mm 1 1 1143d 1143d 0/29 auto-obsoleted due to no activity on 2023/04/10 15:34
upstream INFO: rcu detected stall in kvm_dev_ioctl (3) mm 1 3 2197d 2197d 0/29 closed as invalid on 2020/01/09 08:13
upstream INFO: rcu detected stall in kvm_dev_ioctl mm 1 4 2233d 2234d 0/29 closed as invalid on 2019/12/04 14:04
linux-4.19 BUG: soft lockup in kvm_dev_ioctl 1 1 1708d 1708d 0/1 auto-closed as invalid on 2021/09/08 20:48
android-5-15 BUG: soft lockup in kvm_dev_ioctl 1 1 605d 605d 0/2 auto-obsoleted due to no activity on 2024/08/16 05:28

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4917/1:b..l
	(detected by 1, t=10502 jiffies, g=11505, q=39 ncpus=2)
task:syz.2.128       state:R  running task     stack:22440 pid:4917  ppid:4275   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6873
 irqentry_exit+0x63/0x70 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:lock_acquire+0x20f/0x490 kernel/locking/lockdep.c:5666
Code: 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 0f 85 f5 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 66 43 c7 44 3d 09 00 00 43 c6 44 3d 0b
RSP: 0018:ffffc9000d117aa0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: cbcce70402727000
RDX: 0000000000000000 RSI: ffffffff8a6c1780 RDI: ffffffff8abef920
RBP: ffffc9000d117bb0 R08: dffffc0000000000 R09: fffffbfff2119049
R10: fffffbfff2119049 R11: 1ffffffff2119048 R12: 0000000000000001
R13: 1ffff92001a22f60 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 rcu_read_lock include/linux/rcupdate.h:791 [inline]
 get_obj_cgroup_from_current+0xec/0x280 mm/memcontrol.c:3019
 memcg_slab_pre_alloc_hook mm/slab.h:485 [inline]
 slab_pre_alloc_hook+0x91/0x310 mm/slab.h:715
 slab_alloc_node mm/slub.c:3279 [inline]
 __kmem_cache_alloc_node+0x4f/0x260 mm/slub.c:3398
 kmalloc_trace+0x26/0xe0 mm/slab_common.c:1026
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 kvm_create_vm_debugfs+0x590/0x960 virt/kvm/kvm_main.c:1096
 kvm_create_vm virt/kvm/kvm_main.c:1239 [inline]
 kvm_dev_ioctl_create_vm virt/kvm/kvm_main.c:5010 [inline]
 kvm_dev_ioctl+0x135d/0x1800 virt/kvm/kvm_main.c:5052
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f78e5b8f749
RSP: 002b:00007f78e69a2038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f78e5de5fa0 RCX: 00007f78e5b8f749
RDX: 0000000000000000 RSI: 000000000000ae01 RDI: 0000000000000006
RBP: 00007f78e5c13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f78e5de6038 R14: 00007f78e5de5fa0 R15: 00007fff916133f8
 </TASK>
rcu: rcu_preempt kthread starved for 10533 jiffies! g11505 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:27840 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x2f2/0x1310 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x95/0x380 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:default_idle+0xb/0x10 arch/x86/kernel/process.c:742
Code: 48 89 df e8 a7 b3 b6 f7 e9 4c ff ff ff e8 9d 0e f6 ff 00 00 cc cc 00 00 cc cc 00 00 cc cc 00 66 90 0f 00 2d c7 40 4c 00 fb f4 <c3> 0f 1f 40 00 41 57 41 56 53 49 be 00 00 00 00 00 fc ff df 65 48
RSP: 0018:ffffc90000177de8 EFLAGS: 000002c6
RAX: 9f7627a5cd965200 RBX: ffffffff8a1a6267 RCX: 9f7627a5cd965200
RDX: 0000000000000001 RSI: ffffffff8a6c0600 RDI: ffffffff8abef920
RBP: ffffc90000177f20 R08: dffffc0000000000 R09: ffffed10171e6afa
R10: ffffed10171e6afa R11: 1ffff110171e6af9 R12: 0000000000000001
R13: dffffc0000000000 R14: ffff88813feb1dc0 R15: 1ffffffff1bfe206
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd4e9772a60 CR3: 000000007745f000 CR4: 00000000003526e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 default_idle_call+0x84/0xc0 kernel/sched/idle.c:109
 cpuidle_idle_call kernel/sched/idle.c:191 [inline]
 do_idle+0x1fc/0x570 kernel/sched/idle.c:303
 cpu_startup_entry+0x3f/0x60 kernel/sched/idle.c:401
 start_secondary+0xe4/0xf0 arch/x86/kernel/smpboot.c:281
 secondary_startup_64_no_verify+0xcf/0xdb
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/10 12:34 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in kvm_dev_ioctl
* Struck through repros no longer work on HEAD.