[syzbot] [mm?] INFO: rcu detected stall in sys_unlinkat (3)

[syzbot] [mm?] INFO: rcu detected stall in sys_unlinkat (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    92a09c47464d Linux 6.15-rc5
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=143530f4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=91c351a0f6229e67
dashboard link: https://syzkaller.appspot.com/bug?extid=61ec37db8c428baeb677
compiler:       Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1891731f8dec/disk-92a09c47.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d0de4fa2c8c2/vmlinux-92a09c47.xz
kernel image: https://storage.googleapis.com/syzbot-assets/53a4edfaecf1/bzImage-92a09c47.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+61ec37db8c428baeb677@syzkaller.appspotmail.com

sched: DL replenish lagged too much
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P6265/1:b..l
rcu: 	(detected by 0, t=10503 jiffies, g=19425, q=859 ncpus=2)
task:syz-executor    state:R  running task     stack:22008 pid:6265  tgid:6265  ppid:6251   task_flags:0x400140 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x16e2/0x4cd0 kernel/sched/core.c:6767
 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7090
 irqentry_exit+0x6f/0x90 kernel/entry/common.c:354
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:arch_atomic_read arch/x86/include/asm/atomic.h:23 [inline]
RIP: 0010:raw_atomic_read include/linux/atomic/atomic-arch-fallback.h:457 [inline]
RIP: 0010:atomic_read include/linux/atomic/atomic-instrumented.h:33 [inline]
RIP: 0010:__page_table_check_zero+0x1f9/0x510 mm/page_table_check.c:142
Code: 89 ee e8 fa 26 93 ff 4c 39 ed 0f 84 6c 01 00 00 4c 8b 3d 5a 2c db 0b 4d 01 e7 4c 89 ff be 04 00 00 00 e8 7a 1b f5 ff 4c 89 f8 <48> c1 e8 03 48 b9 00 00 00 00 00 fc ff df 0f b6 04 08 84 c0 0f 85
RSP: 0018:ffffc9000b5ef790 EFLAGS: 00000256
RAX: ffff88801d1b29b8 RBX: 0000000000000000 RCX: ffffffff822cabd6
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff88801d1b29b8
RBP: 0000000000000008 R08: ffff88801d1b29bb R09: 1ffff11003a36537
R10: dffffc0000000000 R11: ffffed1003a36538 R12: ffff88801d1b2970
R13: 0000000000000003 R14: 000000000005d6e9 R15: ffff88801d1b29b8
 page_table_check_free include/linux/page_table_check.h:41 [inline]
 free_pages_prepare mm/page_alloc.c:1263 [inline]
 __free_frozen_pages+0xb22/0xcd0 mm/page_alloc.c:2725
 __slab_free+0x326/0x400 mm/slub.c:4553
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x9a/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_kmalloc+0x22/0xb0 mm/kasan/common.c:385
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4327 [inline]
 __kmalloc_noprof+0x27a/0x4f0 mm/slub.c:4339
 kmalloc_noprof include/linux/slab.h:909 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 tomoyo_encode2 security/tomoyo/realpath.c:45 [inline]
 tomoyo_encode+0x28b/0x550 security/tomoyo/realpath.c:80
 tomoyo_realpath_from_path+0x58d/0x5d0 security/tomoyo/realpath.c:283
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x213/0x4b0 security/tomoyo/file.c:822
 tomoyo_path_rmdir+0xa2/0xe0 security/tomoyo/tomoyo.c:195
 security_path_rmdir+0x167/0x360 security/security.c:1949
 do_rmdir+0x219/0x630 fs/namei.c:4506
 __do_sys_unlinkat fs/namei.c:4683 [inline]
 __se_sys_unlinkat fs/namei.c:4677 [inline]
 __x64_sys_unlinkat+0xc2/0xf0 fs/namei.c:4677
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f36e318df47
RSP: 002b:00007ffdf6aecb78 EFLAGS: 00000207 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 0000000000000065 RCX: 00007f36e318df47
RDX: 0000000000000200 RSI: 00007ffdf6aedd20 RDI: 00000000ffffff9c
RBP: 00007f36e321089d R08: 000055555c96962b R09: 0000000000000000
R10: 0000000000001000 R11: 0000000000000207 R12: 00007ffdf6aedd20
R13: 00007f36e321089d R14: 0000000000033668 R15: 00007ffdf6aeedf0
 </TASK>


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