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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cd9b81672742 Linux 6.1.161
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1397cbfa580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0605c5af04d7603
dashboard link: https://syzkaller.appspot.com/bug?extid=67513229adc33c2c5afc
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/7c7d6fd2ef9f/disk-cd9b8167.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/544b7fd5d4e0/vmlinux-cd9b8167.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3454f19d3753/bzImage-cd9b8167.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+675132...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P33/1:b..l P14563/1:b..l
(detected by 0, t=10502 jiffies, g=116493, q=141 ncpus=2)
task:udevd state:R running task stack:24848 pid:14563 ppid:3637 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:unwind_get_return_address+0x49/0x80 arch/x86/kernel/unwind_orc.c:323
Code: c0 75 47 83 3b 00 74 3a 48 83 c3 48 49 89 df 49 c1 ef 03 43 80 3c 37 00 74 08 48 89 df e8 5f 45 9a 00 48 8b 3b e8 77 27 1d 00 <85> c0 74 14 43 80 3c 37 00 74 08 48 89 df e8 44 45 9a 00 48 8b 03
RSP: 0018:ffffc90004c5f4e8 EFLAGS: 00000202
RAX: 0000000000000001 RBX: ffffc90004c5f550 RCX: 0000000080000000
RDX: ffffc90004c5f501 RSI: dffffc0000000000 RDI: ffffffff81c7cc1e
RBP: ffffc90004c5f590 R08: ffffc90004c5f820 R09: ffffc90004c5f558
R10: dffffc0000000000 R11: fffff5200098bead R12: ffff888018b80000
R13: 1ffff110031700ae R14: dffffc0000000000 R15: 1ffff9200098beaa
arch_stack_walk+0xf2/0x140 arch/x86/kernel/stacktrace.c:26
stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
save_stack+0x121/0x230 mm/page_owner.c:127
__reset_page_owner+0x51/0x1a0 mm/page_owner.c:148
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1459 [inline]
free_pcp_prepare mm/page_alloc.c:1509 [inline]
free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3384
free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3479
free_slab mm/slub.c:2036 [inline]
discard_slab mm/slub.c:2042 [inline]
__unfreeze_partials+0x1a5/0x200 mm/slub.c:2591
put_cpu_partial+0x17c/0x250 mm/slub.c:2667
qlink_free mm/kasan/quarantine.c:168 [inline]
qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
__kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:306
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook+0x4b/0x480 mm/slab.h:737
slab_alloc_node mm/slub.c:3359 [inline]
__kmem_cache_alloc_node+0x140/0x260 mm/slub.c:3398
__do_kmalloc_node mm/slab_common.c:935 [inline]
__kmalloc+0xa0/0x240 mm/slab_common.c:949
kmalloc include/linux/slab.h:568 [inline]
kzalloc include/linux/slab.h:699 [inline]
tomoyo_encode2 security/tomoyo/realpath.c:45 [inline]
tomoyo_encode+0x27e/0x540 security/tomoyo/realpath.c:80
tomoyo_path_perm+0x382/0x610 security/tomoyo/file.c:831
tomoyo_path_symlink+0xa8/0xf0 security/tomoyo/tomoyo.c:199
security_path_symlink+0xdc/0x130 security/security.c:1198
do_symlinkat+0x10c/0x400 fs/namei.c:4503
__do_sys_symlink fs/namei.c:4530 [inline]
__se_sys_symlink fs/namei.c:4528 [inline]
__x64_sys_symlink+0x7a/0x90 fs/namei.c:4528
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f53e0115527
RSP: 002b:00007ffc03aba0d8 EFLAGS: 00000206 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 0000564c63fbee00 RCX: 00007f53e0115527
RDX: fffffffffffffe68 RSI: 00007ffc03aba0e0 RDI: 0000564c63fb7d00
RBP: 0000000000000b3c R08: 0000000000000064 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 00007ffc03aba0e0
R13: 0000564c63fbe410 R14: 0000000000000008 R15: 0000564c63fbee00
</TASK>
task:kworker/u4:2 state:R running task stack:21744 pid:33 ppid:2 flags:0x00004000
Workqueue: bat_events batadv_nc_worker
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:ffffc90000aa7ac0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 5bdce5505b491a00
RDX: 0000000000000000 RSI: ffffffff8a8c23a0 RDI: ffffffff8adf0c20
RBP: ffffc90000aa7bc8 R08: dffffc0000000000 R09: 1ffffffff215e648
R10: dffffc0000000000 R11: fffffbfff215e649 R12: 0000000000000000
R13: 1ffff92000154f64 R14: 0000000000000246 R15: dffffc0000000000
rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
rcu_read_lock include/linux/rcupdate.h:791 [inline]
batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:408 [inline]
batadv_nc_worker+0xeb/0x600 net/batman-adv/network-coding.c:719
process_one_work+0x8a2/0x1160 kernel/workqueue.c:2292
worker_thread+0xaa2/0x1270 kernel/workqueue.c:2439
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
rcu: rcu_preempt kthread starved for 10470 jiffies! g116493 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:26864 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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