[v5.15] INFO: rcu detected stall in do_faccessat (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 29e53a5b1c4f Linux 5.15.194
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=145855e2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb
dashboard link: https://syzkaller.appspot.com/bug?extid=95c5c91e6e23ac315740
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6cf4d5e6e441/disk-29e53a5b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b332ae2ff099/vmlinux-29e53a5b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2f344d06d6b9/bzImage-29e53a5b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+95c5c9...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-....: (1 GPs behind) idle=ca1/1/0x4000000000000002 softirq=41247/41248 fqs=5250
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P12973/1:b..l P5373/1:b..l
(detected by 1, t=10502 jiffies, g=59153, q=307)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 12678 Comm: syz.8.2211 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:check_kcov_mode kernel/kcov.c:172 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x13/0x60 kernel/kcov.c:206
Code: 48 8b 3d 90 cd f1 0b 48 89 de 5b e9 47 9e 43 00 00 00 cc cc 00 00 cc 48 8b 04 24 65 48 8b 0d 64 a5 8a 7e 65 8b 15 65 a5 8a 7e <81> e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 34 16 00 00
RSP: 0018:ffffc9000374eed8 EFLAGS: 00000046
RAX: ffffffff819649f8 RBX: ffffc9000374f080 RCX: ffff888052e83b80
RDX: 0000000000000002 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000374efd0 R08: dffffc0000000000 R09: ffffc9000374f020
R10: fffff520006e9e0b R11: 1ffff920006e9e04 R12: dffffc0000000000
R13: ffffc9000374f086 R14: 0000000000000000 R15: ffffc9000374f240
FS: 00007f95997a56c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4573f802f8 CR3: 0000000052eea000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<TASK>
perf_prepare_sample+0x418/0x1cb0 kernel/events/core.c:7640
__perf_event_output kernel/events/core.c:7802 [inline]
perf_event_output_forward+0x146/0x280 kernel/events/core.c:7822
__perf_event_overflow+0x364/0x530 kernel/events/core.c:9515
perf_swevent_overflow kernel/events/core.c:9591 [inline]
perf_swevent_event+0x4ad/0x530 kernel/events/core.c:9629
perf_tp_event+0x32c/0xb50 kernel/events/core.c:10047
perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10021
perf_trace_preemptirq_template+0x2be/0x380 include/trace/events/preemptirq.h:14
trace_irq_enable_rcuidle+0x108/0x180 include/trace/events/preemptirq.h:40
trace_hardirqs_on+0x57/0x80 kernel/trace/trace_preemptirq.c:44
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x84/0x480 kernel/rcu/tree_plugin.h:674
Code: f1 f1 f1 00 f2 f2 f2 4a 89 04 2b 66 42 c7 44 2b 09 f3 f3 42 c6 44 2b 0b f3 65 44 8b 35 ad 13 9e 7e 41 f7 c6 00 00 f0 00 74 45 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 66 42 c7 44 2b
RSP: 0018:ffffc9000374f680 EFLAGS: 00000206
RAX: cc5e8608a568a200 RBX: 1ffff920006e9ed4 RCX: cc5e8608a568a200
RDX: dffffc0000000000 RSI: ffffffff8a0b1820 RDI: ffffffff8a59a4c0
RBP: ffffc9000374f750 R08: dffffc0000000000 R09: fffffbfff1ff7a1a
R10: fffffbfff1ff7a1a R11: 1ffffffff1ff7a19 R12: ffffffff8c120b00
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
rcu_read_unlock+0x85/0x90 include/linux/rcupdate.h:771
mntput_no_expire+0x292/0x780 fs/namespace.c:-1
mntput fs/namespace.c:1235 [inline]
namespace_unlock+0x344/0x3c0 fs/namespace.c:1454
drop_collected_mounts fs/namespace.c:1939 [inline]
put_mnt_ns+0xdb/0x120 fs/namespace.c:4417
create_new_namespaces+0x621/0x6f0 kernel/nsproxy.c:141
copy_namespaces+0x37d/0x3e0 kernel/nsproxy.c:178
copy_process+0x180f/0x3e00 kernel/fork.c:2293
kernel_clone+0x219/0x930 kernel/fork.c:2679
__do_sys_clone kernel/fork.c:2796 [inline]
__se_sys_clone kernel/fork.c:2780 [inline]
__x64_sys_clone+0x170/0x1c0 kernel/fork.c:2780
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f959b53dec9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f95997a4fe8 EFLAGS: 00000206 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007f959b794fa0 RCX: 00007f959b53dec9
RDX: 0000000000000000 RSI: fffffffffffffd50 RDI: 00000000410a4400
RBP: 00007f959b5c0f91 R08: ffffffffffffffff R09: ffffffffffffffff
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f959b795038 R14: 00007f959b794fa0 R15: 00007fff43f58af8
</TASK>
task:udevd state:R running task stack:23392 pid: 5373 ppid: 3561 flags:0x00004002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6799
irqentry_exit+0x63/0x70 kernel/entry/common.c:432
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__seqprop_spinlock_sequence include/linux/seqlock.h:277 [inline]
RIP: 0010:path_init+0x205/0x1160 fs/namei.c:2341
Code: ed 16 0a 89 ee 83 e6 01 31 ff e8 86 74 ad ff 89 e8 83 e0 01 75 07 e8 1a 71 ad ff eb 40 48 c7 c3 00 47 e1 8b 48 c1 eb 03 f3 90 <42> 0f b6 04 3b 84 c0 75 13 8b 2d ac ed 16 0a 40 f6 c5 01 74 19 e8
RSP: 0018:ffffc9000315fb10 EFLAGS: 00000293
RAX: ffffffff81ca595f RBX: 1ffffffff17c28e0 RCX: ffff888064369dc0
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000006b1b R08: dffffc0000000000 R09: fffffbfff1ff7a19
R10: fffffbfff1ff7a19 R11: 1ffffffff1ff7a18 R12: 1ffff110045a6004
R13: ffffc9000315fcbc R14: ffffc9000315fc80 R15: dffffc0000000000
path_lookupat+0x27/0x440 fs/namei.c:2445
filename_lookup+0x1e2/0x4f0 fs/namei.c:2484
user_path_at_empty+0x40/0x190 fs/namei.c:2883
user_path_at include/linux/namei.h:57 [inline]
do_faccessat+0x3f3/0xa50 fs/open.c:422
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f4ca43c45da
RSP: 002b:00007ffe9532bd28 EFLAGS: 00000206 ORIG_RAX: 00000000000001b7
RAX: ffffffffffffffda RBX: 000000000000000b RCX: 00007f4ca43c45da
RDX: 0000000000000000 RSI: 00007f4ca4a97e2e RDI: 000000000000000b
RBP: 000055a13edd32f0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f4ca4a97e2e R14: 0000000000000000 R15: 0000000000000009
</TASK>
task:modprobe state:R running task stack:27200 pid:12973 ppid: 4978 flags:0x00004002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6799
irqentry_exit+0x63/0x70 kernel/entry/common.c:432
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__seqprop_spinlock_sequence include/linux/seqlock.h:277 [inline]
RIP: 0010:path_init+0x205/0x1160 fs/namei.c:2341
Code: ed 16 0a 89 ee 83 e6 01 31 ff e8 86 74 ad ff 89 e8 83 e0 01 75 07 e8 1a 71 ad ff eb 40 48 c7 c3 00 47 e1 8b 48 c1 eb 03 f3 90 <42> 0f b6 04 3b 84 c0 75 13 8b 2d ac ed 16 0a 40 f6 c5 01 74 19 e8
RSP: 0018:ffffc90003d1f8f8 EFLAGS: 00000293
RAX: ffffffff81ca595f RBX: 1ffffffff17c28e0 RCX: ffff8880501cd940
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000006b1b R08: dffffc0000000000 R09: fffffbfff1ff7a19
R10: fffffbfff1ff7a19 R11: 1ffffffff1ff7a18 R12: 1ffff110045a6444
R13: ffffc90003d1fc7c R14: ffffc90003d1fc40 R15: dffffc0000000000
path_openat+0x18a/0x2f30 fs/namei.c:3737
do_filp_open+0x1b3/0x3e0 fs/namei.c:3769
do_sys_openat2+0x142/0x4a0 fs/open.c:1253
do_sys_open fs/open.c:1269 [inline]
__do_sys_openat fs/open.c:1285 [inline]
__se_sys_openat fs/open.c:1280 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1280
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fb687a530ba
RSP: 002b:00007ffe698ac7c8 EFLAGS: 00000206 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007ffe698ac840 RCX: 00007fb687a530ba
RDX: 0000000000080000 RSI: 00007ffe698ac840 RDI: 00000000ffffff9c
RBP: 00007ffe698ac830 R08: 00007ffe698aca37 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000017
R13: 00007fb687a2f000 R14: 00007ffe698aca50 R15: 0000000000000000
</TASK>


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