WARNING in lookup_slow (4)

Status: moderation: reported on 2025/05/26 09:57
Subsystems: fs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+2b8d9d5c6bae92cffb1d@syzkaller.appspotmail.com
First crash: 450d, last: 18h13m
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
31627deb assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ WARNING in lookup_slow (4) 2026/05/20 10:16 2026/05/20 10:16 2026/05/20 11:00 62fb93a2
d472dc8b repro 💥 WARNING in lookup_slow (4) 2026/03/10 12:19 2026/03/10 12:19 2026/03/10 12:19 5c03941b
Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 WARNING in lookup_slow (2) -1 1 1018d 1018d 0/3 auto-obsoleted due to no activity on 2024/02/09 08:58
upstream WARNING in lookup_slow (2) fs -1 8 792d 824d 0/29 auto-obsoleted due to no activity on 2024/09/12 01:16
linux-6.6 WARNING in lookup_slow -1 1 220d 220d 0/2 auto-obsoleted due to no activity on 2026/04/17 12:20
linux-6.1 WARNING in lookup_slow missing-backport origin:lts-only -1 syz, C inconclusive 10 26d 986d 0/3 upstream: reported C repro on 2023/12/02 22:03
upstream WARNING in lookup_slow (3) fs -1 1 600d 596d 0/29 auto-obsoleted due to no activity on 2025/02/21 12:31
linux-5.15 WARNING in lookup_slow (3) origin:lts-only -1 syz, C error 8 63d 868d 0/3 upstream: reported C repro on 2024/03/30 12:27
upstream WARNING in lookup_slow ntfs3 -1 syz, C error inconclusive 34 935d 1335d 0/29 auto-obsoleted due to no activity on 2024/05/02 19:30
linux-5.15 WARNING in lookup_slow -1 1 1178d 1178d 0/3 auto-obsoleted due to no activity on 2023/09/02 18:27

Sample crash report:
------------[ cut here ]------------
DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem)): count = 0x0, magic = 0xffff888052452d18, owner = 0x0, curr 0xffff88802820dd00, list not empty
WARNING: kernel/locking/rwsem.c:1384 at __up_read+0x6a5/0x930 kernel/locking/rwsem.c:1384, CPU#1: syz.6.849/9074
Modules linked in:
CPU: 1 UID: 0 PID: 9074 Comm: syz.6.849 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:__up_read+0x77d/0x930 kernel/locking/rwsem.c:1384
Code: 8b 49 c7 c2 40 03 ed 8b 4c 0f 44 d0 48 8b 7c 24 28 48 c7 c6 00 03 ed 8b 48 8b 54 24 18 4c 89 e9 4d 89 e0 4c 8b 4c 24 08 41 52 <67> 48 0f b9 3a 48 83 c4 08 e8 c5 a5 2d 03 4c 8b 3c 24 48 8b 5c 24
RSP: 0018:ffffc90010a27858 EFLAGS: 00010246
RAX: ffffffff8bed0360 RBX: 1ffff1100a48a5a4 RCX: ffff888052452d18
RDX: 0000000000000000 RSI: ffffffff8bed0300 RDI: ffffffff905b17f0
RBP: ffffc90010a27930 R08: 0000000000000000 R09: ffff88802820dd00
R10: ffffffff8bed0360 R11: ffffed100a48a5a5 R12: 0000000000000000
R13: ffff888052452d18 R14: ffff888052452d70 R15: ffff888052452d20
FS:  00007fecd34326c0(0000) GS:ffff888125049000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f39fad48000 CR3: 00000000775cd000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 inode_unlock_shared include/linux/fs.h:1049 [inline]
 lookup_slow+0x5e/0x70 fs/namei.c:1937
 walk_component fs/namei.c:2282 [inline]
 link_path_walk+0xd2a/0x1910 fs/namei.c:2656
 path_openat+0x236/0x3830 fs/namei.c:4859
 do_file_open+0x23e/0x4a0 fs/namei.c:4892
 do_sys_openat2+0x115/0x200 fs/open.c:1368
 do_sys_open fs/open.c:1374 [inline]
 __do_sys_openat fs/open.c:1390 [inline]
 __se_sys_openat fs/open.c:1385 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1385
 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: 0033:0x7fecd259e0d9
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:00007fecd3432028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fecd2826090 RCX: 00007fecd259e0d9
RDX: 0000000000000002 RSI: 0000200000000300 RDI: ffffffffffffff9c
RBP: 00007fecd2635024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fecd2826128 R14: 00007fecd2826090 R15: 00007fff5ceeff98
 </TASK>
----------------
Code disassembly (best guess):
   0:	8b 49 c7             	mov    -0x39(%rcx),%ecx
   3:	c2 40 03             	ret    $0x340
   6:	ed                   	in     (%dx),%eax
   7:	8b 4c 0f 44          	mov    0x44(%rdi,%rcx,1),%ecx
   b:	d0 48 8b             	rorb   $1,-0x75(%rax)
   e:	7c 24                	jl     0x34
  10:	28 48 c7             	sub    %cl,-0x39(%rax)
  13:	c6 00 03             	movb   $0x3,(%rax)
  16:	ed                   	in     (%dx),%eax
  17:	8b 48 8b             	mov    -0x75(%rax),%ecx
  1a:	54                   	push   %rsp
  1b:	24 18                	and    $0x18,%al
  1d:	4c 89 e9             	mov    %r13,%rcx
  20:	4d 89 e0             	mov    %r12,%r8
  23:	4c 8b 4c 24 08       	mov    0x8(%rsp),%r9
  28:	41 52                	push   %r10
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	48 83 c4 08          	add    $0x8,%rsp
  33:	e8 c5 a5 2d 03       	call   0x32da5fd
  38:	4c 8b 3c 24          	mov    (%rsp),%r15
  3c:	48                   	rex.W
  3d:	8b                   	.byte 0x8b
  3e:	5c                   	pop    %rsp
  3f:	24                   	.byte 0x24

Crashes (24):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/15 03:07 upstream 2f1baf1fc892 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in lookup_slow
2026/06/09 18:12 upstream 2d3090a8aeb5 c36c07f6 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in lookup_slow
2026/05/02 03:48 upstream ef5f46b63023 753c55b9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root WARNING in lookup_slow
2026/07/04 01:06 upstream d2c9a99135da aa437a8a .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2026/04/26 21:35 upstream 897d54018cc9 9c2d0995 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2026/03/19 21:15 upstream e9825d1c7957 0291cd06 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2026/03/12 16:11 upstream 80234b5ab240 4efadf07 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2026/03/12 09:22 upstream 80234b5ab240 2d88ab01 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2026/02/19 08:52 upstream 956b9cbd7f15 746545b8 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2026/02/16 22:28 upstream 0f2acd3148e0 5d52cba5 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2026/01/16 01:43 upstream 54e82e93ca93 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2026/01/14 17:04 upstream 54e82e93ca93 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2026/01/12 05:41 upstream 54e82e93ca93 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2026/01/06 00:06 upstream 54e82e93ca93 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2025/12/05 11:58 upstream 2061f18ad76e d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2025/10/13 21:30 upstream 3a8660878839 b6605ba8 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2025/09/08 17:33 upstream 76eeb9b8de98 d291dd2d .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2025/08/10 12:23 upstream 561c80369df0 32a0e5ed .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2025/07/22 23:02 upstream 89be9a83ccf1 af30dea9 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2025/07/11 14:08 upstream bc9ff192a6c9 3cda49cf .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2025/06/25 14:44 upstream 7595b66ae9de 26d77996 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2025/06/19 09:02 upstream fb4d33ab452e ed3e87f7 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2025/05/30 12:38 upstream f66bc387efbe 3d2f584d .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
2025/05/22 09:52 upstream d608703fcdd9 0919b50b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in lookup_slow
* Struck through repros no longer work on HEAD.