INFO: rcu detected stall in kernfs_fop_open (2)

Status: upstream: reported on 2026/10/01 09:51
Reported-by: syzbot+6ef287a5e6d33f0b07a5@syzkaller.appspotmail.com
First crash: 2d11h, last: 2d11h
▶ ▼ Similar bugs (11)
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 85d 85d 0/3 upstream: reported on 2026/07/10 06:09
upstream INFO: rcu detected stall in kernfs_fop_open (3) kernfs 1 2 1563d 1613d 0/29 auto-closed as invalid on 2022/09/20 22:08
upstream INFO: rcu detected stall in kernfs_fop_open mm 1 1 2496d 2496d 0/29 closed as invalid on 2019/12/04 14:04
upstream INFO: rcu detected stall in kernfs_fop_open (4) kernel 1 1 1403d 1403d 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 1215d 1215d 0/3 auto-obsoleted due to no activity on 2023/09/14 10:24
upstream INFO: rcu detected stall in kernfs_fop_open (7) prio:high kernfs 1 syz, C error error 18 11d 431d 0/29 upstream: reported C repro on 2025/07/28 23:27
upstream INFO: rcu detected stall in kernfs_fop_open (2) mm 1 1 2460d 2460d 0/29 closed as invalid on 2020/01/09 08:13
linux-6.1 INFO: rcu detected stall in kernfs_fop_open 1 1 586d 586d 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 623d 727d 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 1019d 1065d 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 800d 899d 0/2 auto-obsoleted due to no activity on 2024/10/23 00:09

Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 0-.... } 2680 jiffies s: 90529 root: 0x1/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 15187 Comm: syz.1.2851 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:rcu_dynticks_curr_cpu_in_eqs include/linux/context_tracking.h:122 [inline]
RIP: 0010:rcu_is_watching+0x11/0xa0 kernel/rcu/tree.c:721
Code: f6 e8 d3 d8 d1 02 e9 44 ff ff ff 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 41 57 41 56 53 65 ff 05 6c 45 96 7e e8 1f 73 c6 08 <89> c3 83 f8 08 73 60 49 bf 00 00 00 00 00 fc ff df 4c 8d 34 dd 80
RSP: 0018:ffffc90000007090 EFLAGS: 00000082
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 5a4cc9599b467200
RDX: ffff888054730000 RSI: ffffffff8adf6880 RDI: ffffffff8adf6840
RBP: ffffc900000071f0 R08: ffffc90000007177 R09: ffffc90000007160
R10: dffffc0000000000 R11: fffff52000000e2f R12: 1ffff92000000e28
R13: ffffc90000007240 R14: 0000000000000008 R15: ffff888073a76600
FS:  00007f669f5f66c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fde576f1ff8 CR3: 0000000077b8f000 CR4: 00000000003506f0
DR0: 0000200000000300 DR1: 0000200000000300 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 rcu_read_lock_held_common kernel/rcu/update.c:108 [inline]
 rcu_read_lock_held+0x11/0x40 kernel/rcu/update.c:309
 __perf_output_begin kernel/events/ring_buffer.c:170 [inline]
 perf_output_begin_forward+0x1d1/0xa70 kernel/events/ring_buffer.c:272
 __perf_event_output kernel/events/core.c:7742 [inline]
 perf_event_output_forward+0x1ad/0x2f0 kernel/events/core.c:7760
 __perf_event_overflow+0x457/0x630 kernel/events/core.c:9506
 perf_swevent_overflow+0x19b/0x230 kernel/events/core.c:9589
 perf_swevent_event+0x458/0x570 kernel/events/core.c:-1
 perf_tp_event+0x36b/0xc10 kernel/events/core.c:10074
 perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10042
 perf_trace_preemptirq_template+0x268/0x320 include/trace/events/preemptirq.h:14
 trace_irq_enable_rcuidle+0xd3/0x140 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x24/0x40 kernel/trace/trace_preemptirq.c:44
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:rcu_read_unlock_special+0x7f/0x510 kernel/rcu/tree_plugin.h:685
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 32 7b 95 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc90000007980 EFLAGS: 00000206
RAX: 5a4cc9599b467200 RBX: 1ffff92000000f38 RCX: 5a4cc9599b467200
RDX: dffffc0000000000 RSI: ffffffff8a8c18a0 RDI: ffffffff8adf68a0
RBP: ffffc90000007a80 R08: ffffffff90b0f32f R09: 1ffffffff2161e65
R10: dffffc0000000000 R11: fffffbfff2161e66 R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8e3bb00 R15: 0000000000000001
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
 rcu_read_unlock include/linux/rcupdate.h:823 [inline]
 hsr_announce+0x2ca/0x340 net/hsr/hsr_device.c:427
 call_timer_fn+0x1ac/0x670 kernel/time/timer.c:1701
 expire_timers kernel/time/timer.c:1752 [inline]
 __run_timers+0x56c/0x810 kernel/time/timer.c:2023
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:2036
 handle_softirqs+0x291/0x910 kernel/softirq.c:596
 __do_softirq kernel/softirq.c:630 [inline]
 invoke_softirq kernel/softirq.c:470 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:put_cpu_partial+0x1b0/0x250 mm/slub.c:2666
Code: 3b 44 24 18 0f 85 b4 00 00 00 48 83 c4 20 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 dc 8a 5f 08 f7 c5 00 02 00 00 74 c0 fb 4d 85 e4 <75> bf eb c8 e8 67 1d 40 02 85 c0 0f 84 e9 fe ff ff 83 3d 80 eb 4d
RSP: 0018:ffffc900058a76a8 EFLAGS: 00000246
RAX: 5a4cc9599b467200 RBX: ffff8880174c5000 RCX: 5a4cc9599b467200
RDX: dffffc0000000000 RSI: ffffffff8a8c18a0 RDI: ffffffff8adf68a0
RBP: 0000000000000282 R08: ffffffff90b0f35f R09: 1ffffffff2161e6b
R10: dffffc0000000000 R11: fffffbfff2161e6c R12: 0000000000000000
R13: 0000000000000000 R14: ffff888054730000 R15: ffff8880b8e3f970
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x490 mm/slab.h:737
 slab_alloc_node mm/slub.c:3359 [inline]
 __kmem_cache_alloc_node+0x19d/0x270 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]
 kernfs_fop_open+0x3ce/0xc60 fs/kernfs/file.c:690
 do_dentry_open+0x7dd/0x10b0 fs/open.c:882
 do_open fs/namei.c:3677 [inline]
 path_openat+0x2674/0x2f10 fs/namei.c:3834
 do_filp_open+0x1ee/0x420 fs/namei.c:3861
 do_sys_openat2+0x14b/0x4f0 fs/open.c:1320
 do_sys_open fs/open.c:1336 [inline]
 __do_sys_openat fs/open.c:1352 [inline]
 __se_sys_openat fs/open.c:1347 [inline]
 __x64_sys_openat+0x135/0x160 fs/open.c:1347
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f66a139e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f669f5f6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f66a1625fa0 RCX: 00007f66a139e159
RDX: 0000000000000002 RSI: 00002000000002c0 RDI: 0000000000000006
RBP: 00007f66a143506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f66a1626038 R14: 00007f66a1625fa0 R15: 00007ffdbc057a68
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/01 09:51 linux-6.1.y 1a8763b93150 38f7f0d1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in kernfs_fop_open
* Struck through repros no longer work on HEAD.