syzbot


divide error in qnx6_mmi_fill_super

Status: upstream: reported C repro on 2024/11/01 19:35
Subsystems: ext4
[Documentation on labels]
Reported-by: syzbot+6a0633f11d3fb88860bf@syzkaller.appspotmail.com
First crash: 507d, last: 11d
Cause bisection: introduced by (bisect log) [release commit]:
commit df0cc57e057f18e44dac8e6c18aba47ab53202f9
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date: Sun Jan 9 22:55:34 2022 +0000

  Linux 5.16

Crash: divide error in qnx6_mmi_fill_super (log)
Repro: C syz .config
  
Fix bisection: the issue occurs on the latest tested release (bisect log)
  
Discussions (2)
Title Replies (including bot) Last reply
[PATCH] fix: divide error in qnx6_mmi_fill_super 1 (1) 2024/11/04 05:44
[syzbot] [ext4?] divide error in qnx6_mmi_fill_super 0 (1) 2024/11/01 19:35
Last patch testing requests (10)
Created Duration User Patch Repo Result
2026/02/13 22:50 16m retest repro upstream log
2026/01/30 21:34 19m retest repro upstream report log
2026/01/16 20:28 49m retest repro upstream report log
2026/01/02 19:12 17m retest repro upstream report log
2025/12/04 11:55 18m retest repro upstream report log
2025/11/20 11:28 20m retest repro upstream report log
2025/11/06 10:53 20m retest repro upstream report log
2025/10/23 10:22 19m retest repro upstream report log
2025/09/25 09:06 37m retest repro upstream report log
2025/09/11 08:25 17m retest repro upstream report log

Sample crash report:
loop0: detected capacity change from 0 to 512
Oops: divide error: 0000 [#1] SMP KASAN PTI
CPU: 0 UID: 0 PID: 5960 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:qnx6_mmi_fill_super+0x22d/0x880 fs/qnx6/super_mmi.c:68
Code: c5 28 48 89 e8 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 a9 05 00 00 45 85 e4 8b 45 00 89 c6 0f ce 0f 44 f0 b8 00 10 00 00 31 d2 <f7> f6 89 c5 4c 89 f7 e8 67 8e 40 01 41 89 c6 31 ff 89 c6 e8 1b 90
RSP: 0018:ffffc90003fc7a78 EFLAGS: 00010246
RAX: 0000000000001000 RBX: 0000000000000000 RCX: ffff88803138db80
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff888058072028 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffed1008a0614e R12: 0000000000000000
R13: dffffc0000000000 R14: ffff888037660000 R15: 0000000000000000
FS:  00007f9d62d766c0(0000) GS:ffff88812633f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff674e62000 CR3: 000000002baa2000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 qnx6_fill_super+0x16f/0x1280 fs/qnx6/inode.c:318
 get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694
 vfs_get_tree+0x92/0x2a0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3763 [inline]
 do_new_mount+0x341/0xd30 fs/namespace.c:3839
 do_mount fs/namespace.c:4172 [inline]
 __do_sys_mount fs/namespace.c:4361 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4338
 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: 0033:0x7f9d6371da0a
Code: 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 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:00007f9d62d75e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f9d62d75ee0 RCX: 00007f9d6371da0a
RDX: 0000200000000080 RSI: 0000200000000040 RDI: 00007f9d62d75ea0
RBP: 0000200000000080 R08: 00007f9d62d75ee0 R09: 0000000000808003
R10: 0000000000808003 R11: 0000000000000246 R12: 0000200000000040
R13: 00007f9d62d75ea0 R14: 0000000000000519 R15: 0000200000000000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:qnx6_mmi_fill_super+0x22d/0x880 fs/qnx6/super_mmi.c:68
Code: c5 28 48 89 e8 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 a9 05 00 00 45 85 e4 8b 45 00 89 c6 0f ce 0f 44 f0 b8 00 10 00 00 31 d2 <f7> f6 89 c5 4c 89 f7 e8 67 8e 40 01 41 89 c6 31 ff 89 c6 e8 1b 90
RSP: 0018:ffffc90003fc7a78 EFLAGS: 00010246
RAX: 0000000000001000 RBX: 0000000000000000 RCX: ffff88803138db80
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff888058072028 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffed1008a0614e R12: 0000000000000000
R13: dffffc0000000000 R14: ffff888037660000 R15: 0000000000000000
FS:  00007f9d62d766c0(0000) GS:ffff88812633f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff674e62000 CR3: 000000002baa2000 CR4: 00000000003526f0
----------------
Code disassembly (best guess), 1 bytes skipped:
   0:	28 48 89             	sub    %cl,-0x77(%rax)
   3:	e8 48 c1 e8 03       	call   0x3e8c150
   8:	42 0f b6 04 28       	movzbl (%rax,%r13,1),%eax
   d:	84 c0                	test   %al,%al
   f:	0f 85 a9 05 00 00    	jne    0x5be
  15:	45 85 e4             	test   %r12d,%r12d
  18:	8b 45 00             	mov    0x0(%rbp),%eax
  1b:	89 c6                	mov    %eax,%esi
  1d:	0f ce                	bswap  %esi
  1f:	0f 44 f0             	cmove  %eax,%esi
  22:	b8 00 10 00 00       	mov    $0x1000,%eax
  27:	31 d2                	xor    %edx,%edx
* 29:	f7 f6                	div    %esi <-- trapping instruction
  2b:	89 c5                	mov    %eax,%ebp
  2d:	4c 89 f7             	mov    %r14,%rdi
  30:	e8 67 8e 40 01       	call   0x1408e9c
  35:	41 89 c6             	mov    %eax,%r14d
  38:	31 ff                	xor    %edi,%edi
  3a:	89 c6                	mov    %eax,%esi
  3c:	e8                   	.byte 0xe8
  3d:	1b                   	.byte 0x1b
  3e:	90                   	nop

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/08 12:42 upstream c23719abc330 5cb44a80 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2] ci2-upstream-fs divide error in qnx6_mmi_fill_super
2024/11/12 08:32 upstream 2d5404caa8c7 75bb1b32 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2] ci2-upstream-fs divide error in qnx6_mmi_fill_super
2024/10/28 21:12 upstream 819837584309 9efb3cc7 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2] ci-snapshot-upstream-root divide error in qnx6_mmi_fill_super
2024/10/28 20:37 upstream 819837584309 9efb3cc7 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2] ci-snapshot-upstream-root divide error in qnx6_mmi_fill_super
2024/10/28 20:09 upstream 819837584309 9efb3cc7 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2] ci-snapshot-upstream-root divide error in qnx6_mmi_fill_super
2026/03/08 12:08 upstream c23719abc330 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs divide error in qnx6_mmi_fill_super
2024/10/28 19:25 upstream 819837584309 9efb3cc7 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root divide error in qnx6_mmi_fill_super
* Struck through repros no longer work on HEAD.