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: 104d, last: 14h41m
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
6165e0c0 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ WARNING in filename_mkdirat (2) 2026/06/09 15:36 2026/06/09 15:36 2026/06/09 16:23 c36c07f6
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in filename_mkdirat gfs2 prio:high -1 syz, C 84 126d 209d 29/29 fixed on 2026/05/21 07:50

Sample crash report:
ntfs3(loop9): failed to convert "0080" to macinuit
ntfs3(loop9): failed to convert name for inode 1e.
ntfs3(loop9): ino=1f, mi_enum_attr
ntfs3(loop9): Mark volume as dirty due to NTFS errors
------------[ 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.9.179/7238
WARNING: kernel/locking/rtmutex_common.h:193 at rt_mutex_slowunlock+0x734/0xa30 kernel/locking/rtmutex.c:1432, CPU#1: syz.9.179/7238
Modules linked in:
CPU: 1 UID: 0 PID: 7238 Comm: syz.9.179 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:debug_rt_mutex_unlock kernel/locking/rtmutex_common.h:193 [inline]
RIP: 0010:rt_mutex_slowunlock+0x73b/0xa30 kernel/locking/rtmutex.c:1432
Code: b2 8f 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 cf 02 00 00 83 3d b9 54 59 04 00 75 13 48 8d 3d 1c 47 5c 04 48 c7 c6 60 2a 6d 8b <67> 48 0f b9 3a 90 e9 cf f9 ff ff 48 8d 3d 13 47 5c 04 67 48 0f b9
RSP: 0018:ffffc90004917ce0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff888044ee6ee0 RCX: 0000000000080000
RDX: ffffc90006f61000 RSI: ffffffff8b6d2a60 RDI: ffffffff8fb50a30
RBP: ffffc90004917dd0 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1f642f9 R12: dffffc0000000000
R13: 1ffff92000922fa4 R14: ffff888044ee6e90 R15: 0000000000000246
FS:  00007fc2725266c0(0000) GS:ffff888125ccb000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb8a8bb3000 CR3: 0000000021fba000 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:120 [inline]
 end_creating_path fs/namei.c:5132 [inline]
 filename_mkdirat+0x309/0x520 fs/namei.c:5448
 __do_sys_mkdirat fs/namei.c:5464 [inline]
 __se_sys_mkdirat+0x35/0x150 fs/namei.c:5461
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc2742ce159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fc272526028 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007fc274555fa0 RCX: 00007fc2742ce159
RDX: 00000000000001ff RSI: 0000200000000000 RDI: ffffffffffffff9c
RBP: 00007fc27436503b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc274556038 R14: 00007fc274555fa0 R15: 00007ffca96a3128
 </TASK>
----------------
Code disassembly (best guess):
   0:	b2 8f                	mov    $0x8f,%dl
   2:	48 c1 e8 03          	shr    $0x3,%rax
   6:	42 0f b6 04 20       	movzbl (%rax,%r12,1),%eax
   b:	84 c0                	test   %al,%al
   d:	0f 85 cf 02 00 00    	jne    0x2e2
  13:	83 3d b9 54 59 04 00 	cmpl   $0x0,0x45954b9(%rip)        # 0x45954d3
  1a:	75 13                	jne    0x2f
  1c:	48 8d 3d 1c 47 5c 04 	lea    0x45c471c(%rip),%rdi        # 0x45c473f
  23:	48 c7 c6 60 2a 6d 8b 	mov    $0xffffffff8b6d2a60,%rsi
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	90                   	nop
  30:	e9 cf f9 ff ff       	jmp    0xfffffa04
  35:	48 8d 3d 13 47 5c 04 	lea    0x45c4713(%rip),%rdi        # 0x45c474f
  3c:	67                   	addr32
  3d:	48                   	rex.W
  3e:	0f                   	.byte 0xf
  3f:	b9                   	.byte 0xb9

Crashes (19):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/14 02:27 upstream d681d7ef617e 70a60e12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING in filename_mkdirat
2026/08/05 12:52 upstream c21bb4193868 b3eac40e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root WARNING in filename_mkdirat
2026/08/03 17:47 upstream 075b74841bd0 a68cb31b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root WARNING in filename_mkdirat
2026/07/09 19:10 upstream 2c7c88a412aa a0c310a3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING in filename_mkdirat
2026/07/07 04:17 upstream 0e35b9b6ec0f 8e71ce95 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING in filename_mkdirat
2026/07/06 08:51 upstream 8cdeaa50eae8 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING in filename_mkdirat
2026/06/26 20:28 upstream 51cb1aa1250c fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING in filename_mkdirat
2026/06/24 20:37 upstream 840ef6c78e6a 302586aa .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs WARNING in filename_mkdirat
2026/08/23 02:04 upstream 818bebeb63dd 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
2026/07/27 00:40 upstream 4235cb24ec1e 492bab15 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
2026/07/16 09:26 upstream 37e2f878a7a6 851bd571 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
2026/07/14 11:56 upstream 3b029c035b34 2130f682 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
2026/07/09 09:48 upstream 0e35b9b6ec0f b9f1ceaa .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
2026/07/04 20:28 upstream 1e9cdc2ea15a fcece630 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
2026/07/04 10:59 upstream 71dfdfb0209b fcece630 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
2026/07/03 16:23 upstream d2c9a99135da aa437a8a .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
2026/06/30 17:06 upstream dc59e4fea9d8 e5173a01 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
2026/06/26 14:11 upstream 4edcdefd4083 7ff32d8b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in filename_mkdirat
2026/06/02 16:31 upstream 6f3ed7fec72f 62fe1528 .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.