syzbot


WARNING in filename_mkdirat

Status: moderation: reported on 2026/02/14 13:23
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+8e725133f14f47d38632@syzkaller.appspotmail.com
First crash: 5d17h, last: 1d04h

Sample crash report:
------------[ 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

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/11 18:51 upstream 192c0159402e 75707236 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING in filename_mkdirat
2026/02/10 13:21 upstream 72c395024dac 91d776d3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING in filename_mkdirat
2026/02/15 02:10 upstream 3e48a11675c5 1e62d198 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
2026/02/14 16:25 upstream 770aaedb461a 1e62d198 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
2026/02/13 20:54 upstream cee73b1e840c 1e62d198 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
2026/02/13 02:52 upstream 37a93dd5c49b 504cb1bf .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
2026/02/11 14:05 upstream 192c0159402e 75707236 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
* Struck through repros no longer work on HEAD.