[syzbot] [overlayfs?] WARNING in end_dirop

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d8ba32c5a460 Merge tag 'block-6.19-20251218' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15b11392580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1f2b6fe1fdf1a00b
dashboard link: https://syzkaller.appspot.com/bug?extid=19b2d871b77d222db434
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/aea104204e52/disk-d8ba32c5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/84e31eb35609/vmlinux-d8ba32c5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8598104810a4/bzImage-d8ba32c5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+19b2d8...@syzkaller.appspotmail.com

------------[ cut here ]------------
DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current)
WARNING: kernel/locking/rtmutex_common.h:182 at debug_rt_mutex_unlock kernel/locking/rtmutex_common.h:182 [inline], CPU#1: syz.4.151/6765
WARNING: kernel/locking/rtmutex_common.h:182 at rt_mutex_slowunlock+0x6c0/0x8a0 kernel/locking/rtmutex.c:1419, CPU#1: syz.4.151/6765
Modules linked in:
CPU: 1 UID: 0 PID: 6765 Comm: syz.4.151 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:debug_rt_mutex_unlock kernel/locking/rtmutex_common.h:182 [inline]
RIP: 0010:rt_mutex_slowunlock+0x6c7/0x8a0 kernel/locking/rtmutex.c:1419
Code: db 8e 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 c0 01 00 00 83 3d 7d ea 05 04 00 75 13 48 8d 3d 00 ea 08 04 48 c7 c6 60 1e eb 8a <67> 48 0f b9 3a 90 e9 35 fa ff ff 90 0f 0b 90 e9 59 fe ff ff be 02
RSP: 0018:ffffc9000f52f4c0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff88805ddef6f0 RCX: ffff88801df5bc80
RDX: 0000000000000000 RSI: ffffffff8aeb1e60 RDI: ffffffff8ede4300
RBP: ffffc9000f52f5b0 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1db686f R12: dffffc0000000000
R13: ffff88805ddef6a0 R14: 0000000000000a06 R15: 1ffff92001ea5ea0
FS: 00007f64ba31e6c0(0000) GS:ffff888126e01000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000005c8c0000 CR4: 00000000003526f0
Call Trace:
<TASK>
inode_unlock include/linux/fs.h:1037 [inline]
end_dirop+0x7d/0x90 fs/namei.c:2888
end_creating_keep include/linux/namei.h:147 [inline]
ovl_workdir_create+0x4c7/0x900 fs/overlayfs/super.c:346
ovl_make_workdir fs/overlayfs/super.c:682 [inline]
ovl_get_workdir fs/overlayfs/super.c:840 [inline]
ovl_fill_super_creds fs/overlayfs/super.c:1453 [inline]
ovl_fill_super+0x188f/0x5a90 fs/overlayfs/super.c:1567
vfs_get_super fs/super.c:1324 [inline]
get_tree_nodev+0xbb/0x150 fs/super.c:1343
vfs_get_tree+0x92/0x2a0 fs/super.c:1751
fc_mount fs/namespace.c:1199 [inline]
do_new_mount_fc fs/namespace.c:3636 [inline]
do_new_mount+0x302/0xa10 fs/namespace.c:3712
do_mount fs/namespace.c:4035 [inline]
__do_sys_mount fs/namespace.c:4224 [inline]
__se_sys_mount+0x313/0x410 fs/namespace.c:4201
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f64bc0bf749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f64ba31e038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f64bc315fa0 RCX: 00007f64bc0bf749
RDX: 0000200000000b80 RSI: 0000200000000100 RDI: 0000000000000000
RBP: 00007f64bc143f91 R08: 0000200000000240 R09: 0000000000000000
R10: 0000000000000008 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f64bc316038 R14: 00007f64bc315fa0 R15: 00007ffc96aee038
</TASK>
----------------
Code disassembly (best guess):
0: db 8e 48 c1 e8 03 fisttpl 0x3e8c148(%rsi)
6: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax
b: 84 c0 test %al,%al
d: 0f 85 c0 01 00 00 jne 0x1d3
13: 83 3d 7d ea 05 04 00 cmpl $0x0,0x405ea7d(%rip) # 0x405ea97
1a: 75 13 jne 0x2f
1c: 48 8d 3d 00 ea 08 04 lea 0x408ea00(%rip),%rdi # 0x408ea23
23: 48 c7 c6 60 1e eb 8a mov $0xffffffff8aeb1e60,%rsi
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: 90 nop
30: e9 35 fa ff ff jmp 0xfffffa6a
35: 90 nop
36: 0f 0b ud2
38: 90 nop
39: e9 59 fe ff ff jmp 0xfffffe97
3e: be .byte 0xbe
3f: 02 .byte 0x2


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