[v6.1] INFO: rcu detected stall in __fput

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 228da13e907e Linux 6.1.175
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17a468ae580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4dd3c1715f0a309b
dashboard link: https://syzkaller.appspot.com/bug?extid=31fd09a6f69d194fabaa
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a1730af56ab4/disk-228da13e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/eafe9b37a422/vmlinux-228da13e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7353ac7f337a/bzImage-228da13e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+31fd09...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P3640/1:b..l
(detected by 0, t=10502 jiffies, g=9657, q=181 ncpus=2)
task:udevd state:R running task stack:25168 pid:3640 ppid:1 flags:0x00004002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5245 [inline]
__schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6874
irqentry_exit+0x63/0x70 kernel/entry/common.c:439
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:lock_acquire+0x225/0x4a0 kernel/locking/lockdep.c:5666
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3d 04 f8 0f 85 f0 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 43 c7 44 3d 08 00 00 00 00 65 48 8b 04
RSP: 0018:ffffc900032b7c20 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 5deb4b5b9d6a2d00
RDX: 0000000000000000 RSI: ffffffff8a8c2c20 RDI: ffffffff8adf2060
RBP: ffffc900032b7d30 R08: dffffc0000000000 R09: 1ffffffff215fe48
R10: dffffc0000000000 R11: fffffbfff215fe49 R12: 0000000000000001
R13: 1ffff92000656f90 R14: 0000000000000246 R15: dffffc0000000000
rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
rcu_read_lock include/linux/rcupdate.h:791 [inline]
dput+0x53/0x1d0 fs/dcache.c:904
__fput+0x5e0/0x920 fs/file_table.c:328
task_work_run+0x1d0/0x260 kernel/task_work.c:203
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f60e5ea7407
RSP: 002b:00007ffde1fc6fb0 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 00007f60e65fc880 RCX: 00007f60e5ea7407
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000000000c
RBP: 00007f60e65fc6e8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000016
R13: 00000000ffffffff R14: ffffffffffffffff R15: 00007ffde1fc72b0
</TASK>
rcu: rcu_preempt kthread starved for 9994 jiffies! g9657 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:28016 pid:16 ppid:2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5245 [inline]
__schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
schedule+0xb9/0x180 kernel/sched/core.c:6638
schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2168
rcu_gp_fqs_loop+0x303/0x1340 kernel/rcu/tree.c:1706
rcu_gp_kthread+0x99/0x3b0 kernel/rcu/tree.c:1905
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</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 default_idle+0xb/0x10 arch/x86/kernel/process.c:741


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