syzbot
WARNING in filename_mkdirat (2)
Status:
moderation: reported on 2026/06/06 16:43
Subsystems:
fs
Labels:
prio:high
[Documentation on labels]
Reported-by: syzbot+a3453db58a98d7809020@syzkaller.appspotmail.com
First crash: 54d, last: 10d
Sample crash report:
------------[ cut here ]------------
DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current)
WARNING: kernel/locking/rtmutex_common.h:193 at debug_rt_mutex_unlock kernel/locking/rtmutex_common.h:193 [inline], CPU#1: syz.1.334/8044
WARNING: kernel/locking/rtmutex_common.h:193 at rt_mutex_slowunlock+0x732/0xa20 kernel/locking/rtmutex.c:1432, CPU#1: syz.1.334/8044
Modules linked in:
CPU: 1 UID: 0 PID: 8044 Comm: syz.1.334 Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:debug_rt_mutex_unlock kernel/locking/rtmutex_common.h:193 [inline]
RIP: 0010:rt_mutex_slowunlock+0x739/0xa20 kernel/locking/rtmutex.c:1432
Code: af 8f 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 cf 02 00 00 83 3d db 23 6c 04 00 75 13 48 8d 3d 3e 68 6f 04 48 c7 c6 a0 ff 6c 8b <67> 48 0f b9 3a 90 e9 d1 f9 ff ff 48 8d 3d 35 68 6f 04 67 48 0f b9
RSP: 0018:ffffc90005c1fce0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff888060c0c7f8 RCX: 0000000000080000
RDX: ffffc900114fe000 RSI: ffffffff8b6cffa0 RDI: ffffffff8fb2d3b0
RBP: ffffc90005c1fdd0 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1f5f1e9 R12: dffffc0000000000
R13: 1ffff92000b83fa4 R14: ffff888060c0c7a8 R15: 0000000000000246
FS: 00007f2620f746c0(0000) GS:ffff888125d4a000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2359541000 CR3: 000000004d1f2000 CR4: 00000000003526f0
Call Trace:
<TASK>
inode_unlock include/linux/fs.h:1034 [inline]
end_dirop fs/namei.c:2955 [inline]
end_creating include/linux/namei.h:117 [inline]
end_creating_path fs/namei.c:4995 [inline]
filename_mkdirat+0x309/0x520 fs/namei.c:5314
__do_sys_mkdirat fs/namei.c:5330 [inline]
__se_sys_mkdirat+0x35/0x150 fs/namei.c:5327
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2622d5ccc7
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:00007f2620f73e58 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007f2620f73ee0 RCX: 00007f2622d5ccc7
RDX: 00000000000001ff RSI: 00002000000000c0 RDI: 00000000ffffff9c
RBP: 0000000000000000 R08: 0000200000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00002000000000c0
R13: 00007f2620f73ea0 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 cf 02 00 00 jne 0x2e0
11: 83 3d db 23 6c 04 00 cmpl $0x0,0x46c23db(%rip) # 0x46c23f3
18: 75 13 jne 0x2d
1a: 48 8d 3d 3e 68 6f 04 lea 0x46f683e(%rip),%rdi # 0x46f685f
21: 48 c7 c6 a0 ff 6c 8b mov $0xffffffff8b6cffa0,%rsi
* 28: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2d: 90 nop
2e: e9 d1 f9 ff ff jmp 0xfffffa04
33: 48 8d 3d 35 68 6f 04 lea 0x46f6835(%rip),%rdi # 0x46f686f
3a: 67 addr32
3b: 48 rex.W
3c: 0f .byte 0xf
3d: b9 .byte 0xb9
* Struck through repros no longer work on HEAD.