INFO: rcu detected stall in kernfs_fop_open (7)

Status: upstream: reported C repro on 2025/07/28 23:27
Subsystems: kernfs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+19d01f6082ec61dd45b2@syzkaller.appspotmail.com
First crash: 446d, last: 12d
Cause bisection: failed (error log, bisect log)
  
Fix bisection: failed (error log, bisect log)
  
▶ ▼ ✨ AI Patch Versions (3)
Version Stage Reported Report Link Job
1 upstream 2026/08/13 02:15 Discussion 37f064ee-e021-43aa-8cfc-9f2a5a7c35d7
2 moderation 2026/07/22 18:32 Discussion 37f064ee-e021-43aa-8cfc-9f2a5a7c35d7
1 moderation 2026/06/26 22:21 Discussion e96ce5ef-50a8-4856-a518-279d5610b23c
▶ ▼ ✨ AI Jobs (4)
ID Workflow Result Correct Bug Created Started Finished Revision
37f064ee patch-iteration ✅ INFO: rcu detected stall in kernfs_fop_open (7) 2026/07/22 17:53 2026/07/22 17:53 2026/07/22 18:32 44995053
7faf1502 patch-iteration 💥 INFO: rcu detected stall in kernfs_fop_open (7) 2026/07/22 11:12 2026/07/22 11:12 2026/07/22 11:51 14117f8f
e96ce5ef patching ❓ INFO: rcu detected stall in kernfs_fop_open (7) 2026/06/26 19:51 2026/06/26 19:51 2026/06/26 22:21 7ff32d8b
f682a53c assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ INFO: rcu detected stall in kernfs_fop_open (7) 2026/05/21 16:18 2026/05/21 16:18 2026/05/21 17:13 d5742584
▶ ▼ Discussions (15)
Title Replies (including bot) Last reply
[PATCH net v3] net/sched: taprio: catch up in bounded time when the schedule falls behind 2 (2) 2026/09/03 00:36
[syzbot] [kernfs?] [mm?] INFO: rcu detected stall in kernfs_fop_open (7) 2 (6) 2026/09/01 07:45
[PATCH net v2 3/3] selftests/tc-testing: taprio: add case for the software minimum interval 3 (3) 2026/08/31 07:31
Re: [PATCH net v2 2/3] net/sched: taprio: enforce a minimum interval for software schedules 2 (2) 2026/08/31 07:30
[PATCH net v2 1/3] net/sched: taprio: catch up in bounded time when the schedule falls behind 3 (3) 2026/08/31 07:30
[PATCH net v2 0/3] net/sched: taprio: fix software schedule livelocks 2 (2) 2026/08/20 06:27
[PATCH net v2 2/3] net/sched: taprio: enforce a minimum interval for software schedules 1 (1) 2026/08/20 06:27
[PATCH net 0/3] net/sched: taprio: fix software schedule livelocks 5 (5) 2026/08/19 07:50
[PATCH net 3/3] selftests/tc-testing: taprio: add case for the software minimum interval 1 (1) 2026/08/18 07:17
[PATCH net 2/3] net/sched: taprio: enforce a minimum interval for software schedules 1 (1) 2026/08/18 07:17
[PATCH] net/sched: taprio: enforce minimum software scheduling interval 4 (4) 2026/08/17 00:35
[syzbot] Monthly kernfs report (Aug 2026) 0 (1) 2026/08/02 00:00
[syzbot] Monthly kernfs report (Jul 2026) 0 (1) 2026/07/01 12:32
[syzbot] Monthly kernfs report (May 2026) 0 (1) 2026/05/31 04:32
[syzbot] Monthly mm report (May 2026) 0 (1) 2026/05/23 12:32
▶ ▼ Similar bugs (10)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in kernfs_fop_open (2) 1 1 73d 73d 0/3 upstream: reported on 2026/07/10 06:09
upstream INFO: rcu detected stall in kernfs_fop_open (3) kernfs 1 2 1551d 1601d 0/29 auto-closed as invalid on 2022/09/20 22:08
upstream INFO: rcu detected stall in kernfs_fop_open mm 1 1 2483d 2483d 0/29 closed as invalid on 2019/12/04 14:04
upstream INFO: rcu detected stall in kernfs_fop_open (4) kernel 1 1 1390d 1390d 0/29 auto-obsoleted due to no activity on 2023/03/09 20:29
linux-5.15 INFO: rcu detected stall in kernfs_fop_open 1 1 1203d 1203d 0/3 auto-obsoleted due to no activity on 2023/09/14 10:24
upstream INFO: rcu detected stall in kernfs_fop_open (2) mm 1 1 2448d 2447d 0/29 closed as invalid on 2020/01/09 08:13
linux-6.1 INFO: rcu detected stall in kernfs_fop_open 1 1 573d 573d 0/3 auto-obsoleted due to no activity on 2025/06/04 16:10
upstream INFO: rcu detected stall in kernfs_fop_open (6) mm 1 17 610d 715d 0/29 auto-obsoleted due to no activity on 2025/04/18 13:25
upstream INFO: rcu detected stall in kernfs_fop_open (5) cgroups 1 2 1007d 1053d 0/29 auto-obsoleted due to no activity on 2024/03/18 04:35
android-5-15 BUG: soft lockup in kernfs_fop_open 1 7 788d 887d 0/2 auto-obsoleted due to no activity on 2024/10/23 00:09
▶ ▼ Last patch testing requests (8)
Created Duration User Patch Repo Result
2026/09/01 01:41 1h37m junjie.cao@intel.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git abdf623ddb75b24659018d3952d8f61937306ae5 OK job log log
2026/08/31 08:40 27m junjie.cao@intel.com patch git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git a8455260b2e9c024d1872ac1c094793d55a7e537 error job log
2026/08/11 13:42 1h07m junjie.cao@linux.dev patch git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git dd057113ac7ba5bdd2aed3d9405305911152f911 OK job log log
2026/07/14 08:18 26m retest repro upstream log
2026/04/29 22:37 1h02m retest repro upstream report log
2026/03/25 04:53 26m retest repro linux-next no crash log
2026/01/10 13:28 24m retest repro linux-next report log
2025/08/16 12:59 19m retest repro upstream report log
▶ ▼ Fix bisection attempts (5)
Created Duration User Patch Repo Result
2026/02/18 07:53 1m bisect fix upstream error job log
2025/12/17 04:53 6h42m bisect fix upstream OK (0) job log log
2025/11/15 20:42 3h45m bisect fix upstream OK (0) job log log
2025/10/11 17:10 2h36m bisect fix upstream OK (0) job log log
2025/09/09 21:30 3h45m bisect fix upstream OK (0) job log log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (1 ticks this GP) idle=375c/1/0x4000000000000000 softirq=18409/18409 fqs=0
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5512/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=12441, q=623 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 5955 Comm: udevd Not tainted 6.16.0-rc7-syzkaller-00034-g25fae0b93d1d #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:hlock_class kernel/locking/lockdep.c:234 [inline]
RIP: 0010:__lock_acquire+0xa4f/0xd20 kernel/locking/lockdep.c:5237
Code: e5 ff 90 0f 0b 90 90 90 31 c0 48 8b 3c 24 48 83 78 40 00 0f 84 8c 02 00 00 41 8b 46 20 25 ff 1f 00 00 48 0f a3 05 f1 3a 09 12 <73> 10 48 69 c0 c8 00 00 00 48 8d 80 f0 82 48 93 eb 40 83 3d 38 ca
RSP: 0018:ffffc90000007b70 EFLAGS: 00000003
RAX: 000000000000006d RBX: 0000000000000001 RCX: 00000000ab2b819a
RDX: 00000000001bf57d RSI: 00000000f5f6d907 RDI: ffff888061b90000
RBP: 0000000000000001 R08: 0000000000000000 R09: ffffffff81ae7962
R10: dffffc0000000000 R11: fffffbfff1f43b9f R12: 000000000000006e
R13: ffff888061b90af0 R14: ffff888061b90b18 R15: 4d4df099ab2b819a
FS:  00007fe3e1610880(0000) GS:ffff888125c23000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f509ec85f98 CR3: 0000000032c5c000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
 _raw_spin_lock_irq+0xa2/0xf0 kernel/locking/spinlock.c:170
 __run_hrtimer kernel/time/hrtimer.c:1765 [inline]
 __hrtimer_run_queues+0x602/0xc60 kernel/time/hrtimer.c:1825
 hrtimer_interrupt+0x45b/0xaa0 kernel/time/hrtimer.c:1887
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1039 [inline]
 __sysvec_apic_timer_interrupt+0x108/0x410 arch/x86/kernel/apic/apic.c:1056
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1050
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:native_save_fl arch/x86/include/asm/irqflags.h:26 [inline]
RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:109 [inline]
RIP: 0010:arch_local_irq_save arch/x86/include/asm/irqflags.h:127 [inline]
RIP: 0010:lock_acquire+0xc9/0x360 kernel/locking/lockdep.c:5867
Code: 01 11 85 c0 0f 85 eb 00 00 00 65 48 8b 04 25 08 d0 9f 92 83 b8 ec 0a 00 00 00 0f 85 d5 00 00 00 48 c7 44 24 30 00 00 00 00 9c <8f> 44 24 30 4c 89 74 24 10 4d 89 fe 4c 8b 7c 24 30 fa 48 c7 c7 20
RSP: 0018:ffffc90003197290 EFLAGS: 00000246
RAX: ffff888061b90000 RBX: 0000000000000000 RCX: 0d0c881f9d5e1900
RDX: 0000000000000000 RSI: ffffffff8172ab02 RDI: 1ffffffff1c27e1c
RBP: ffffffff8172aae5 R08: 0000000000000000 R09: 0000000000000000
R10: ffffc90003197458 R11: ffffffff81acfe40 R12: 0000000000000002
R13: ffffffff8e13f0e0 R14: 0000000000000000 R15: 0000000000000000
 rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 rcu_read_lock include/linux/rcupdate.h:841 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1155 [inline]
 unwind_next_frame+0xc2/0x2390 arch/x86/kernel/unwind_orc.c:479
 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __kmalloc_cache_noprof+0x230/0x3d0 mm/slub.c:4359
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 kernfs_fop_open+0x397/0xca0 fs/kernfs/file.c:623
 do_dentry_open+0xdf0/0x1970 fs/open.c:964
 vfs_open+0x3b/0x340 fs/open.c:1094
 do_open fs/namei.c:3896 [inline]
 path_openat+0x2ee5/0x3830 fs/namei.c:4055
 do_filp_open+0x1fa/0x410 fs/namei.c:4082
 do_sys_openat2+0x121/0x1c0 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_openat fs/open.c:1468 [inline]
 __se_sys_openat fs/open.c:1463 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1463
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe3e0ea7407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffe447dd8f0 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fe3e1610880 RCX: 00007fe3e0ea7407
RDX: 0000000000080000 RSI: 00007ffe447dda70 RDI: ffffffffffffff9c
RBP: 0000000000000008 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000556b9eca17f5
R13: 0000556b9eca17f5 R14: 0000000000000001 R15: 0000556b9ecbc140
 </TASK>
task:dhcpcd          state:R  running task     stack:21384 pid:5512  tgid:5512  ppid:5511   task_flags:0x400140 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5397 [inline]
 __schedule+0x16fd/0x4cf0 kernel/sched/core.c:6786
 preempt_schedule_common+0x83/0xd0 kernel/sched/core.c:6966
 preempt_schedule+0xae/0xc0 kernel/sched/core.c:6990
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock_irqrestore+0xfd/0x110 kernel/locking/spinlock.c:194
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 __wake_up_common_lock+0x190/0x1f0 kernel/sched/wait.c:108
 sock_def_readable+0x1fb/0x550 net/core/sock.c:3583
 unix_dgram_sendmsg+0xd78/0x17d0 net/unix/af_unix.c:2236
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:727
 sock_write_iter+0x258/0x330 net/socket.c:1131
 do_iter_readv_writev+0x56b/0x7f0 fs/read_write.c:-1
 vfs_writev+0x31a/0x960 fs/read_write.c:1057
 do_writev+0x14d/0x2d0 fs/read_write.c:1103
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f810cb46407
RSP: 002b:00007ffd0761b7f0 EFLAGS: 00000202 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f810cabc740 RCX: 00007f810cb46407
RDX: 0000000000000002 RSI: 00007ffd0761b890 RDI: 000000000000000b
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000000000000000b
R13: 00007f810cabc6c8 R14: 0000000000000000 R15: 00007ffd0762b9a0
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g12441 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=4027
rcu: rcu_preempt kthread starved for 10502 jiffies! g12441 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=0
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:I stack:27128 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5397 [inline]
 __schedule+0x16fd/0x4cf0 kernel/sched/core.c:6786
 __schedule_loop kernel/sched/core.c:6864 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6879
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2054
 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2256
 kthread+0x70e/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Crashes (16):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/24 23:14 upstream 25fae0b93d1d fb8f743d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in kernfs_fop_open
2026/09/08 21:25 upstream 5acbae5f7eb3 243b72f1 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in kernfs_fop_open
2026/06/27 05:13 upstream 51cb1aa1250c fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in kernfs_fop_open
2026/06/15 22:21 upstream 0e0611827f33 50bb0618 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kernfs_fop_open
2026/03/11 04:11 upstream b4f0dd314b39 86914af9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kernfs_fop_open
2026/01/19 07:33 upstream 24d479d26b25 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in kernfs_fop_open
2025/07/31 23:35 upstream 260f6f4fda93 0c075d67 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kernfs_fop_open
2025/07/02 11:34 upstream 66701750d556 ffe4b334 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in kernfs_fop_open
2026/07/27 11:27 upstream f5098b6bae76 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: rcu detected stall in kernfs_fop_open
2026/08/20 16:29 net 564973a259ec 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in kernfs_fop_open
2026/08/12 11:38 net cba9ccb47e9f f8d35649 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in kernfs_fop_open
2026/07/26 05:36 net 53658c6f3682 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in kernfs_fop_open
2026/05/21 19:26 net 0377bd2722c1 e195359d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in kernfs_fop_open
2026/05/18 13:23 net aaec7096f996 55156e84 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in kernfs_fop_open
2026/08/28 23:51 net-next 1b78070aaef6 bcbc8ceb .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in kernfs_fop_open
2025/12/27 12:50 linux-next cc3aa43b44bd d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in kernfs_fop_open
* Struck through repros no longer work on HEAD.