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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 01879f56bdde Linux 5.15.190
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16c16312580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4bfb7f3ca9a4e172
dashboard link: https://syzkaller.appspot.com/bug?extid=b3a32ce67979d738bb8d
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/47310f1c8692/disk-01879f56.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d4d20855b227/vmlinux-01879f56.xz
kernel image: https://storage.googleapis.com/syzbot-assets/958809b6d16d/bzImage-01879f56.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b3a32c...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P4199/2:b..l
(detected by 1, t=10502 jiffies, g=11641, q=275)
task:udevd state:R running task stack:24784 pid: 4199 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:__sanitizer_cov_trace_pc+0x0/0x60 kernel/kcov.c:202
Code: 66 2e 0f 1f 84 00 00 00 00 00 53 48 89 fb e8 17 00 00 00 48 8b 3d 30 c4 f1 0b 48 89 de 5b e9 67 9c 43 00 00 00 cc cc 00 00 cc <48> 8b 04 24 65 48 8b 0d 04 a5 8a 7e 65 8b 15 05 a5 8a 7e 81 e2 00
RSP: 0018:ffffc90002f0f808 EFLAGS: 00000202
RAX: 0000000000032601 RBX: 0000000000000001 RCX: 817f271b67ec5200
RDX: 0000000000000000 RSI: ffffffff8a59a220 RDI: ffffffff8a59a1e0
RBP: dffffc0000000000 R08: dffffc0000000000 R09: fffffbfff1ff7619
R10: fffffbfff1ff7619 R11: 1ffffffff1ff7618 R12: 0000000000001000
R13: dffffc0000000000 R14: 0000000000001c0a R15: 0000000000000ffe
rcu_read_lock include/linux/rcupdate.h:740 [inline]
prepend_path+0x1fc/0xbb0 fs/d_path.c:169
d_absolute_path+0x9e/0x140 fs/d_path.c:235
tomoyo_get_absolute_path security/tomoyo/realpath.c:101 [inline]
tomoyo_realpath_from_path+0x331/0x610 security/tomoyo/realpath.c:276
tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
tomoyo_path_perm+0x1cd/0x510 security/tomoyo/file.c:822
security_inode_getattr+0xcf/0x120 security/security.c:1348
vfs_getattr+0x26/0x3a0 fs/stat.c:157
vfs_statx+0x149/0x4d0 fs/stat.c:225
vfs_fstatat fs/stat.c:243 [inline]
__do_sys_newfstatat fs/stat.c:411 [inline]
__se_sys_newfstatat fs/stat.c:405 [inline]
__x64_sys_newfstatat+0x12c/0x1b0 fs/stat.c:405
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: 0033:0x7ff445a48b0a
RSP: 002b:00007ffd5a07e1c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 0000000000006180 RCX: 00007ff445a48b0a
RDX: 00007ffd5a07e1f0 RSI: 000056538f6be190 RDI: 00000000ffffff9c
RBP: 0000000000000000 R08: 0000000000000000 R09: 000056538f6b1450
R10: 0000000000000100 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 000056538f6be190 R15: 000056538f6adfa0
</TASK>
rcu: rcu_preempt kthread starved for 9232 jiffies! g11641 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->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:R running task stack:28032 pid: 15 ppid: 2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_timeout+0x15c/0x280 kernel/time/timer.c:1914
rcu_gp_fqs_loop+0x29e/0x11b0 kernel/rcu/tree.c:1972
rcu_gp_kthread+0x98/0x350 kernel/rcu/tree.c:2145
kthread+0x436/0x520 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 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:729


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