syzbot


general protection fault in ocfs2_dx_dir_lookup_rec

Status: upstream: reported C repro on 2026/01/09 06:42
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+f6ffc1909131398c8dc4@syzkaller.appspotmail.com
First crash: 12d, last: 8d12h
Bug presence (2)
Date Name Commit Repro Result
2026/01/13 linux-5.15.y (ToT) 68efe5a6c16a C [report] general protection fault in ocfs2_dx_dir_lookup_rec
2026/01/13 upstream (ToT) b71e635feefc C Didn't crash
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-out-of-bounds Read in ocfs2_dx_dir_lookup_rec ocfs2 19 C 76 139d 419d 29/29 fixed on 2025/09/04 16:57
upstream KASAN: use-after-free Read in ocfs2_dx_dir_lookup_rec ocfs2 19 C 14 58d 115d 29/29 fixed on 2026/01/07 12:29

Sample crash report:
general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 PID: 5002 Comm: syz.1.134 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:ocfs2_dx_dir_lookup_rec+0x3a0/0x780 fs/ocfs2/dir.c:812
Code: 28 48 89 44 24 38 48 83 c3 40 48 89 d8 48 c1 e8 03 42 80 3c 20 00 74 08 48 89 df e8 8a cd a5 fe 4c 8b 33 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 bf 02 00 00 41 8b 1f 48 8b 7c 24 20 48
RSP: 0018:ffffc90003fef520 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88805a79b378 RCX: ffff88807a6b8000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88805a79b360
RBP: ffffc90003fef630 R08: ffffc90003fef690 R09: ffffc90003fef69c
R10: 0000000000000002 R11: 0000000000000000 R12: dffffc0000000000
R13: ffffc90003fef698 R14: 0000000000000041 R15: 0000000000000000
FS:  00007f0ed06b36c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffcd24b4bb8 CR3: 000000002b089000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ocfs2_dx_dir_lookup+0xd8/0x510 fs/ocfs2/dir.c:860
 ocfs2_dx_dir_search fs/ocfs2/dir.c:920 [inline]
 ocfs2_find_entry_dx fs/ocfs2/dir.c:1034 [inline]
 ocfs2_find_entry+0xfb1/0x1f90 fs/ocfs2/dir.c:1071
 ocfs2_find_files_on_disk+0xdb/0x2f0 fs/ocfs2/dir.c:1995
 ocfs2_lookup_ino_from_name+0x4f/0xf0 fs/ocfs2/dir.c:2017
 ocfs2_lookup+0x241/0x930 fs/ocfs2/namei.c:122
 lookup_one_qstr_excl+0x10e/0x240 fs/namei.c:1571
 filename_create+0x21e/0x450 fs/namei.c:3844
 do_mknodat+0x16e/0x620 fs/namei.c:3989
 __do_sys_mknod fs/namei.c:4035 [inline]
 __se_sys_mknod fs/namei.c:4033 [inline]
 __x64_sys_mknod+0x8a/0xa0 fs/namei.c:4033
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f0ed1044749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f0ed06b3038 EFLAGS: 00000246 ORIG_RAX: 0000000000000085
RAX: ffffffffffffffda RBX: 00007f0ed129afa0 RCX: 00007f0ed1044749
RDX: 0000000000000000 RSI: 0000000000001000 RDI: 0000200000000080
RBP: 00007f0ed10c8f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f0ed129b038 R14: 00007f0ed129afa0 R15: 00007ffecc9335b8
 </TASK>
Modules linked in:
---[ end trace 06824b2ec18a08ed ]---
RIP: 0010:ocfs2_dx_dir_lookup_rec+0x3a0/0x780 fs/ocfs2/dir.c:812
Code: 28 48 89 44 24 38 48 83 c3 40 48 89 d8 48 c1 e8 03 42 80 3c 20 00 74 08 48 89 df e8 8a cd a5 fe 4c 8b 33 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 20 84 c0 0f 85 bf 02 00 00 41 8b 1f 48 8b 7c 24 20 48
RSP: 0018:ffffc90003fef520 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88805a79b378 RCX: ffff88807a6b8000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88805a79b360
RBP: ffffc90003fef630 R08: ffffc90003fef690 R09: ffffc90003fef69c
R10: 0000000000000002 R11: 0000000000000000 R12: dffffc0000000000
R13: ffffc90003fef698 R14: 0000000000000041 R15: 0000000000000000
FS:  00007f0ed06b36c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f572973a000 CR3: 000000002b089000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	28 48 89             	sub    %cl,-0x77(%rax)
   3:	44 24 38             	rex.R and $0x38,%al
   6:	48 83 c3 40          	add    $0x40,%rbx
   a:	48 89 d8             	mov    %rbx,%rax
   d:	48 c1 e8 03          	shr    $0x3,%rax
  11:	42 80 3c 20 00       	cmpb   $0x0,(%rax,%r12,1)
  16:	74 08                	je     0x20
  18:	48 89 df             	mov    %rbx,%rdi
  1b:	e8 8a cd a5 fe       	call   0xfea5cdaa
  20:	4c 8b 33             	mov    (%rbx),%r14
  23:	4c 89 f8             	mov    %r15,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 0f b6 04 20       	movzbl (%rax,%r12,1),%eax <-- trapping instruction
  2f:	84 c0                	test   %al,%al
  31:	0f 85 bf 02 00 00    	jne    0x2f6
  37:	41 8b 1f             	mov    (%r15),%ebx
  3a:	48 8b 7c 24 20       	mov    0x20(%rsp),%rdi
  3f:	48                   	rex.W

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/09 11:50 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan general protection fault in ocfs2_dx_dir_lookup_rec
2026/01/09 08:54 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan general protection fault in ocfs2_dx_dir_lookup_rec
2026/01/09 07:45 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan general protection fault in ocfs2_dx_dir_lookup_rec
2026/01/09 06:41 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan general protection fault in ocfs2_dx_dir_lookup_rec
2026/01/09 10:11 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2] ci2-linux-5-15-kasan general protection fault in ocfs2_dx_dir_lookup_rec
* Struck through repros no longer work on HEAD.