[moderation] [fs?] WARNING in filename_mkdirat

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 192c0159402e Merge tag 'powerpc-7.0-1' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=107b1a52580000
kernel config: https://syzkaller.appspot.com/x/.config?x=3ca778c8a7bffc62
dashboard link: https://syzkaller.appspot.com/bug?extid=8e725133f14f47d38632
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/74e830cc9aab/disk-192c0159.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/29489398e43c/vmlinux-192c0159.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8c645f91ae19/bzImage-192c0159.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8e7251...@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#0: syz.3.148/6721
WARNING: kernel/locking/rtmutex_common.h:182 at rt_mutex_slowunlock+0x6d9/0x8b0 kernel/locking/rtmutex.c:1419, CPU#0: syz.3.148/6721
Modules linked in:
CPU: 0 UID: 0 PID: 6721 Comm: syz.3.148 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:debug_rt_mutex_unlock kernel/locking/rtmutex_common.h:182 [inline]
RIP: 0010:rt_mutex_slowunlock+0x6e0/0x8b0 kernel/locking/rtmutex.c:1419
Code: 49 8f 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 c0 01 00 00 83 3d 14 9b 35 04 00 75 13 48 8d 3d b7 9e 38 04 48 c7 c6 80 04 2d 8b <67> 48 0f b9 3a 90 e9 2a fa ff ff 90 0f 0b 90 e9 4c fe ff ff be 02
RSP: 0018:ffffc90006677ce0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff88805ee9d830 RCX: 0000000000080000
RDX: ffffc9000e26d000 RSI: ffffffff8b2d0480 RDI: ffffffff8f4c11a0
RBP: ffffc90006677dd0 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1e921bf R12: dffffc0000000000
R13: 1ffff92000ccefa4 R14: 0000000000000246 R15: ffff88805ee9d7e0
FS: 00007fab53d466c0(0000) GS:ffff88812659c000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000011158000 CR4: 00000000003526f0
Call Trace:
<TASK>
inode_unlock include/linux/fs.h:1038 [inline]
end_dirop fs/namei.c:2947 [inline]
end_creating include/linux/namei.h:126 [inline]
end_creating_path fs/namei.c:4962 [inline]
filename_mkdirat+0x309/0x520 fs/namei.c:5271
__do_sys_mkdirat fs/namei.c:5287 [inline]
__se_sys_mkdirat+0x35/0x150 fs/namei.c:5284
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fab55aeae57
Code: 00 66 90 48 89 f2 b9 00 01 00 00 48 89 fe bf 9c ff ff ff e9 db f7 ff ff 66 2e 0f 1f 84 00 00 00 00 00 90 b8 02 01 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fab53d45e58 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007fab53d45ee0 RCX: 00007fab55aeae57
RDX: 00000000000001ff RSI: 00002000000000c0 RDI: 00000000ffffff9c
RBP: 0000000000000000 R08: 0000200000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00002000000000c0
R13: 00007fab53d45ea0 R14: 0000000000000000 R15: 0000000000000000
</TASK>
----------------
Code disassembly (best guess), 2 bytes skipped:
0: 48 c1 e8 03 shr $0x3,%rax
4: 42 0f b6 04 20 movzbl (%rax,%r12,1),%eax
9: 84 c0 test %al,%al
b: 0f 85 c0 01 00 00 jne 0x1d1
11: 83 3d 14 9b 35 04 00 cmpl $0x0,0x4359b14(%rip) # 0x4359b2c
18: 75 13 jne 0x2d
1a: 48 8d 3d b7 9e 38 04 lea 0x4389eb7(%rip),%rdi # 0x4389ed8
21: 48 c7 c6 80 04 2d 8b mov $0xffffffff8b2d0480,%rsi
* 28: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2d: 90 nop
2e: e9 2a fa ff ff jmp 0xfffffa5d
33: 90 nop
34: 0f 0b ud2
36: 90 nop
37: e9 4c fe ff ff jmp 0xfffffe88
3c: be .byte 0xbe
3d: 02 .byte 0x2


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