[v5.15] INFO: rcu detected stall in sys_inotify_add_watch

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 003148680b79 Linux 5.15.177
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1588de18580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f2c956168ff5b89
dashboard link: https://syzkaller.appspot.com/bug?extid=8ae89eb0014464963da4
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/452e6089e1b8/disk-00314868.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/368807beca93/vmlinux-00314868.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e98b52fba46c/bzImage-00314868.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8ae89e...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P8492/1:b..l
(detected by 0, t=10502 jiffies, g=50177, q=110)
task:udevd state:R running task stack:23616 pid: 8492 ppid: 3546 flags:0x00004002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5027 [inline]
__schedule+0x12c4/0x45b0 kernel/sched/core.c:6373
preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6777
irqentry_exit+0x53/0x80 kernel/entry/common.c:432
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__sanitizer_cov_trace_switch+0x2e/0xe0 kernel/kcov.c:328
Code: 41 54 53 48 8b 46 08 48 83 c0 f8 48 c1 c0 3d 48 83 f8 07 0f 87 ac 00 00 00 b9 8b 00 00 00 0f a3 c1 0f 83 9e 00 00 00 4c 8b 16 <4d> 85 d2 0f 84 92 00 00 00 4c 8b 04 c5 20 eb ae 8a 4c 8b 4c 24 20
RSP: 0018:ffffc90002f3f9f8 EFLAGS: 00000297
RAX: 0000000000000000 RBX: 0000000000000064 RCX: 000000000000008b
RDX: 0000000000000000 RSI: ffffffff8cc147d0 RDI: 0000000000000064
RBP: ffffc90002f3fb60 R08: 0000000000000001 R09: ffffffff81d9b582
R10: 0000000000000002 R11: ffff88807ed1d940 R12: dffffc0000000000
R13: ffffc90002f3fc40 R14: ffff888024be3321 R15: ffff888024be3321
link_path_walk+0x112/0xd90 fs/namei.c:2230
path_lookupat+0xa9/0x450 fs/namei.c:2454
filename_lookup+0x230/0x5c0 fs/namei.c:2484
user_path_at_empty+0x40/0x180 fs/namei.c:2883
user_path_at include/linux/namei.h:57 [inline]
inotify_find_inode fs/notify/inotify/inotify_user.c:370 [inline]
__do_sys_inotify_add_watch fs/notify/inotify/inotify_user.c:769 [inline]
__se_sys_inotify_add_watch+0x1a3/0xf00 fs/notify/inotify/inotify_user.c:722
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f151777dee7
RSP: 002b:00007ffc1209f5d8 EFLAGS: 00000202 ORIG_RAX: 00000000000000fe
RAX: ffffffffffffffda RBX: 000055e7d1c7d740 RCX: 00007f151777dee7
RDX: 0000000000000008 RSI: 000055e7d1c6f7b0 RDI: 0000000000000007
RBP: 000055e7d1c7ccd0 R08: 0000000000000001 R09: 69eb4efc4e23858b
R10: 00000000000001b6 R11: 0000000000000202 R12: 000055e7d1c8b640
R13: 000055e7d1c6c060 R14: 0000000000000008 R15: 000055e7d1c5b910
</TASK>
rcu: rcu_preempt kthread starved for 10532 jiffies! g50177 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:26488 pid: 15 ppid: 2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5027 [inline]
__schedule+0x12c4/0x45b0 kernel/sched/core.c:6373
schedule+0x11b/0x1f0 kernel/sched/core.c:6456
schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1914
rcu_gp_fqs_loop+0x2bf/0x1080 kernel/rcu/tree.c:1972
rcu_gp_kthread+0xa4/0x360 kernel/rcu/tree.c:2145
kthread+0x3f6/0x4f0 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_safe_halt drivers/acpi/processor_idle.c:108 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_idle_do_entry+0x10f/0x340 drivers/acpi/processor_idle.c:562


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.