[v5.15] INFO: rcu detected stall in getdents64

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 241d66fa280c Linux 5.15.208
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12154e73980000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=f0d4cdcfe0c420bd584b
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/d3e9d10633a1/disk-241d66fa.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/beca1f713e4b/vmlinux-241d66fa.xz
kernel image: https://storage.googleapis.com/syzbot-assets/26a15a6e1c14/bzImage-241d66fa.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f0d4cd...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 1-...0: (1 GPs behind) idle=259/1/0x4000000000000000 softirq=24271/24273 fqs=2095
(detected by 0, t=10506 jiffies, g=34349, q=944)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 3561 Comm: udevd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
RIP: 0010:_raw_spin_lock_irqsave+0xa5/0x100 kernel/locking/spinlock.c:162
Code: f8 fa 41 f7 c6 00 02 00 00 74 05 e8 a5 1f b9 f7 bf 01 00 00 00 e8 db 2b 8c f7 48 8d 7b 18 31 f6 31 d2 31 c9 41 b8 01 00 00 00 <45> 31 c9 ff 75 08 e8 d0 cb 96 f7 48 83 c4 08 48 89 df e8 d4 21 98
RSP: 0018:ffffc90000dd0c40 EFLAGS: 00000046
RAX: 0000000000010002 RBX: ffffffff964f7ee0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff964f7ef8
RBP: ffffc90000dd0cd8 R08: 0000000000000001 R09: ffff8880233c1b40
R10: dffffc0000000000 R11: ffffed100467836b R12: dffffc0000000000
R13: ffff8880233c1b40 R14: 0000000000000806 R15: 1ffff920001ba188
FS: 00007fafddd3b880(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000303 CR3: 0000000029e2c000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
debug_object_deactivate+0x62/0x390 lib/debugobjects.c:749
debug_hrtimer_deactivate kernel/time/hrtimer.c:415 [inline]
__run_hrtimer kernel/time/hrtimer.c:1653 [inline]
__hrtimer_run_queues+0x2b9/0xb70 kernel/time/hrtimer.c:1749
hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1811
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
__sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
</IRQ>
<TASK>
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 50 c4 10 0c 48 89 de 5b e9 27 55 44 00 00 00 cc cc 00 00 cc <48> 8b 04 24 65 48 8b 0d a4 39 89 7e 65 8b 15 a5 39 89 7e 81 e2 00
RSP: 0018:ffffc90002dafd20 EFLAGS: 00000202
RAX: 0000000000000002 RBX: dffffc0000000000 RCX: 0000000000000007
RDX: ffffffff81ed76a4 RSI: ffffffff8c450460 RDI: 000000007fffffff
RBP: ffff888074568f30 R08: ffff88807da05940 R09: 0000000000000002
R10: 0000000000000001 R11: 0000000000000000 R12: ffff888062998298
R13: ffffc90002dafe60 R14: 000000007fffffff R15: 1ffff1100c533053
dir_emit_dots include/linux/fs.h:3728 [inline]
kernfs_fop_readdir+0x197/0x7e0 fs/kernfs/dir.c:1723
iterate_dir+0x218/0x560 fs/readdir.c:-1
__do_sys_getdents64 fs/readdir.c:369 [inline]
__se_sys_getdents64+0xf2/0x270 fs/readdir.c:354
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: 0033:0x7fafdde72d23
Code: 8b 05 d9 00 10 00 64 c7 00 16 00 00 00 31 c0 eb b0 66 0f 1f 44 00 00 b8 ff ff ff 7f 48 39 c2 48 0f 47 d0 b8 d9 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 05 c3 0f 1f 40 00 48 8b 15 a1 00 10 00 f7 d8
RSP: 002b:00007ffe910bfbf8 EFLAGS: 00000293 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 000055ce767d8370 RCX: 00007fafdde72d23
RDX: 0000000000008000 RSI: 000055ce767d83a0 RDI: 000000000000000d
RBP: 000055ce767d8374 R08: 00007fafddf73ac0 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000293 R12: 000055ce767d83a0
R13: fffffffffffffe68 R14: 0000000000000002 R15: 00007ffe910bfea0
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup