INFO: rcu detected stall in inotify_add_watch

Status: upstream: reported syz repro on 2026/01/19 19:56
Subsystems: fs modules
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+aa5520f7faf8d5438034@syzkaller.appspotmail.com
First crash: 202d, last: 172d
Cause bisection: failed (error log, bisect log)
  
Fix bisection: failed (error log, bisect log)
  
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ID Workflow Result Correct Bug Created Started Finished Revision
e045a4ed assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ INFO: rcu detected stall in inotify_add_watch 2026/05/23 23:35 2026/05/23 23:35 2026/05/24 00:20 c69befb3
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Title Replies (including bot) Last reply
[syzbot] [modules?] INFO: rcu detected stall in inotify_add_watch 0 (1) 2026/01/19 19:56
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in inotify_add_watch 1 2 310d 329d 0/3 auto-obsoleted due to no activity on 2026/01/07 19:37
upstream INFO: rcu detected stall in sys_inotify_add_watch (3) fs 1 2 541d 613d 0/29 auto-obsoleted due to no activity on 2025/05/12 13:24
linux-5.15 INFO: rcu detected stall in sys_inotify_add_watch 1 1 557d 557d 0/3 auto-obsoleted due to no activity on 2025/05/05 23:52
upstream INFO: rcu detected stall in sys_inotify_add_watch (2) lsm 1 1 729d 729d 0/29 auto-obsoleted due to no activity on 2024/11/04 18:18
upstream INFO: rcu detected stall in sys_inotify_add_watch fs 1 1 1784d 1784d 0/29 auto-closed as invalid on 2021/12/16 04:51
▶ ▼ Last patch testing requests (4)
Created Duration User Patch Repo Result
2026/08/04 16:07 33m retest repro upstream report log
2026/05/25 22:28 32m retest repro upstream log
2026/05/25 22:15 25m retest repro upstream log
2026/01/29 22:50 21m retest repro upstream report log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P12/2:b..l P6218/1:b..l P5834/1:b..l
rcu: 	(detected by 1, t=10503 jiffies, g=14653, q=1024 ncpus=2)
task:udevd           state:R  running task     stack:24568 pid:5834  tgid:5834  ppid:5196   task_flags:0x440140 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x149b/0x4fd0 kernel/sched/core.c:6863
 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7190
 irqentry_exit+0x5e3/0x670 kernel/entry/common.c:216
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:rcu_read_lock include/linux/rcupdate.h:868 [inline]
RIP: 0010:class_rcu_constructor include/linux/rcupdate.h:1195 [inline]
RIP: 0010:is_module_text_address+0x44/0x1e0 kernel/module/main.c:3856
Code: 00 00 00 48 c7 c7 a0 1a f4 8d 31 f6 31 d2 b9 02 00 00 00 45 31 c0 45 31 c9 53 e8 77 82 f2 ff 48 83 c4 08 e8 4e 5a ae 09 85 c0 <74> 3a e8 85 91 fb ff 84 c0 75 31 e8 3c 5a ae 09 85 c0 74 28 80 3d
RSP: 0018:ffffc90002ff7920 EFLAGS: 00000202
RAX: 0000000000000001 RBX: ffffffff81ab6c1d RCX: ffff88807bec3d00
RDX: 00000000706f5022 RSI: ffffffff8d976a6b RDI: ffffffff8bc086e0
RBP: 0000000000000001 R08: ffffffff81ab6c1d R09: ffffffff8df41aa0
R10: dffffc0000000000 R11: ffffffff81acf4d0 R12: ffff88807bec3d00
R13: ffff88805500bc80 R14: 00007f1b687219a7 R15: 1ffff920005fef3e
 kernel_text_address+0x94/0xe0 kernel/extable.c:119
 __kernel_text_address+0xd/0x40 kernel/extable.c:79
 unwind_get_return_address+0x4d/0x90 arch/x86/kernel/unwind_orc.c:385
 arch_stack_walk+0xfc/0x150 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4953 [inline]
 slab_alloc_node mm/slub.c:5263 [inline]
 kmem_cache_alloc_noprof+0x37d/0x710 mm/slub.c:5270
 inotify_new_watch fs/notify/inotify/inotify_user.c:599 [inline]
 inotify_update_watch fs/notify/inotify/inotify_user.c:647 [inline]
 __do_sys_inotify_add_watch fs/notify/inotify/inotify_user.c:781 [inline]
 __se_sys_inotify_add_watch+0x6d4/0xf10 fs/notify/inotify/inotify_user.c:729
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1b687219a7
RSP: 002b:00007fffd4df20d8 EFLAGS: 00000206 ORIG_RAX: 00000000000000fe
RAX: ffffffffffffffda RBX: 0000558f453876d0 RCX: 00007f1b687219a7
RDX: 0000000000000008 RSI: 0000558f45371360 RDI: 0000000000000007
RBP: 0000558f45360910 R08: 00000000000001d0 R09: 0000000000000003
R10: 0000000000000000 R11: 0000000000000206 R12: 0000558f453876d0
R13: 0000558f4536e190 R14: 0000000000000008 R15: 0000558f453876d0
 </TASK>
task:kworker/u8:17   state:R  running task     stack:24568 pid:6218  tgid:6218  ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: events_unbound cfg80211_wiphy_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x149b/0x4fd0 kernel/sched/core.c:6863
 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7190
 irqentry_exit+0x5e3/0x670 kernel/entry/common.c:216
 asm_sysvec_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:lock_release+0x2d8/0x3b0 kernel/locking/lockdep.c:5893
Code: 33 e2 10 00 00 00 00 eb b5 e8 d4 9e bb 09 f7 c3 00 02 00 00 74 b9 65 48 8b 05 c4 ed e1 10 48 3b 44 24 28 75 44 fb 48 83 c4 30 <5b> 41 5c 41 5d 41 5e 41 5f 5d e9 94 1e 72 ff cc 48 8d 3d 71 4a e7
RSP: 0018:ffffc9000257f3e0 EFLAGS: 00000282
RAX: 0526f4b768dc6600 RBX: 0000000000000202 RCX: 0000000000000046
RDX: 0000000000000003 RSI: ffffffff8d976a6b RDI: ffffffff8bc086e0
RBP: ffff88802d8e2a28 R08: ffffc9000257fa20 R09: ffffc9000257f538
R10: dffffc0000000000 R11: fffff520004afea9 R12: 0000000000000003
R13: 0000000000000003 R14: ffffffff8df41aa0 R15: ffff88802d8e1e80
 rcu_lock_release include/linux/rcupdate.h:341 [inline]
 rcu_read_unlock include/linux/rcupdate.h:897 [inline]
 class_rcu_destructor include/linux/rcupdate.h:1195 [inline]
 unwind_next_frame+0x1ab1/0x23d0 arch/x86/kernel/unwind_orc.c:695
 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:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2540 [inline]
 slab_free mm/slub.c:6670 [inline]
 kmem_cache_free+0x197/0x620 mm/slub.c:6781
 skb_release_data+0x62d/0x7c0 net/core/skbuff.c:1107
 skb_release_all net/core/skbuff.c:1182 [inline]
 __kfree_skb net/core/skbuff.c:1196 [inline]
 sk_skb_reason_drop+0x127/0x170 net/core/skbuff.c:1234
 kfree_skb_reason include/linux/skbuff.h:1322 [inline]
 kfree_skb include/linux/skbuff.h:1331 [inline]
 ieee80211_iface_work+0xb2a/0x12d0 net/mac80211/iface.c:1792
 cfg80211_wiphy_work+0x2ab/0x450 net/wireless/core.c:438
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
task:kworker/u8:0    state:R  running task     stack:24480 pid:12    tgid:12    ppid:2      task_flags:0x4208160 flags:0x00080000
Workqueue: ipv6_addrconf addrconf_dad_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x149b/0x4fd0 kernel/sched/core.c:6863
 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7190
 irqentry_exit+0x5e3/0x670 kernel/entry/common.c:216
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:lock_release+0x2d8/0x3b0 kernel/locking/lockdep.c:5893
Code: 33 e2 10 00 00 00 00 eb b5 e8 d4 9e bb 09 f7 c3 00 02 00 00 74 b9 65 48 8b 05 c4 ed e1 10 48 3b 44 24 28 75 44 fb 48 83 c4 30 <5b> 41 5c 41 5d 41 5e 41 5f 5d e9 94 1e 72 ff cc 48 8d 3d 71 4a e7
RSP: 0018:ffffc90000116f20 EFLAGS: 00000282
RAX: ccca9c3ae3660b00 RBX: 0000000000000202 RCX: 0000000000000046
RDX: 0000000000000005 RSI: ffffffff8d976a6b RDI: ffffffff8bc086e0
RBP: ffff88801c2a6778 R08: ffffc900001175b8 R09: ffffc90000117078
R10: dffffc0000000000 R11: fffff52000022e11 R12: 0000000000000005
R13: 0000000000000005 R14: ffffffff8df41aa0 R15: ffff88801c2a5b80
 rcu_lock_release include/linux/rcupdate.h:341 [inline]
 rcu_read_unlock include/linux/rcupdate.h:897 [inline]
 class_rcu_destructor include/linux/rcupdate.h:1195 [inline]
 unwind_next_frame+0x1ab1/0x23d0 arch/x86/kernel/unwind_orc.c:695
 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:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x3e2/0x700 mm/slub.c:5776
 kmalloc_noprof include/linux/slab.h:957 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 ref_tracker_alloc+0x133/0x460 lib/ref_tracker.c:271
 __netdev_tracker_alloc include/linux/netdevice.h:4400 [inline]
 netdev_hold include/linux/netdevice.h:4429 [inline]
 dst_init+0xd9/0x450 net/core/dst.c:52
 dst_alloc+0x12a/0x170 net/core/dst.c:93
 ip6_dst_alloc net/ipv6/route.c:342 [inline]
 icmp6_dst_alloc+0x75/0x420 net/ipv6/route.c:3333
 mld_sendpack+0x683/0xe60 net/ipv6/mcast.c:1844
 ipv6_mc_dad_complete+0x88/0x410 net/ipv6/mcast.c:2279
 addrconf_dad_completed+0x6d5/0xd60 net/ipv6/addrconf.c:4340
 addrconf_dad_work+0xc36/0x14b0 net/ipv6/addrconf.c:-1
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
rcu: rcu_preempt kthread starved for 10628 jiffies! g14653 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:27480 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x149b/0x4fd0 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6960
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:82
Code: 1e 84 b6 f5 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 53 91 0e 00 f3 0f 1e fa fb f4 <e9> f3 83 b6 f5 cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90000197e20 EFLAGS: 000002c6
RAX: 00000000000f3f43 RBX: ffffffff8197149e RCX: 0000000080000001
RDX: 0000000000000001 RSI: ffffffff8d792d31 RDI: ffffffff8bc086e0
RBP: ffffc90000197f10 R08: ffff8880b87336db R09: 1ffff110170e66db
R10: dffffc0000000000 R11: ffffed10170e66dc R12: ffffffff8f822470
R13: 1ffff1100385fb70 R14: 0000000000000001 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff888125f1f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe5546e0f98 CR3: 000000002efbb000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:767
 default_idle_call+0x73/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:191 [inline]
 do_idle+0x1be/0x4d0 kernel/sched/idle.c:332
 cpu_startup_entry+0x44/0x60 kernel/sched/idle.c:430
 start_secondary+0x101/0x110 arch/x86/kernel/smpboot.c:312
 common_startup_64+0x13e/0x147
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/15 19:54 upstream 944aacb68baf d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in inotify_add_watch
2026/02/14 14:59 upstream c22e26bd0906 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in inotify_add_watch
* Struck through repros no longer work on HEAD.