[v5.15] divide error in flush_commit_list (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 68efe5a6c16a Linux 5.15.197
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17bb3f14580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7e6ed99963d6ee1d
dashboard link: https://syzkaller.appspot.com/bug?extid=4d57aae26d1d48fdbc5e
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/900f9b9bd850/disk-68efe5a6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1e089a5019a6/vmlinux-68efe5a6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b319f477b907/bzImage-68efe5a6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4d57aa...@syzkaller.appspotmail.com

divide error: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 5078 Comm: kworker/1:15 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: reiserfs/loop3 flush_async_commits
RIP: 0010:flush_commit_list+0xb5f/0x1d70 fs/reiserfs/journal.c:1049
Code: df 42 0f b6 0c 21 84 c9 0f 85 be 01 00 00 49 83 c5 17 4c 89 e9 48 c1 e9 03 42 0f b6 0c 21 84 c9 0f 85 d5 01 00 00 8b 0b 31 d2 <48> f7 f1 48 89 d3 49 83 c6 18 4c 89 f0 48 c1 e8 03 42 80 3c 20 00
RSP: 0018:ffffc9000337faa0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8880511e7014 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff8880511e700f
RBP: ffffc9000337fc08 R08: dffffc0000000000 R09: fffff520007a0282
R10: fffff520007a0282 R11: 1ffff920007a0281 R12: dffffc0000000000
R13: ffff8880511e7017 R14: ffff88807419f000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4871c81f98 CR3: 0000000029b78000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
flush_async_commits+0xa0/0xc0 fs/reiserfs/journal.c:3552
process_one_work+0x863/0x1000 kernel/workqueue.c:2310
worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
Modules linked in:
---[ end trace e9b1b850ff9432bc ]---
RIP: 0010:flush_commit_list+0xb5f/0x1d70 fs/reiserfs/journal.c:1049
Code: df 42 0f b6 0c 21 84 c9 0f 85 be 01 00 00 49 83 c5 17 4c 89 e9 48 c1 e9 03 42 0f b6 0c 21 84 c9 0f 85 d5 01 00 00 8b 0b 31 d2 <48> f7 f1 48 89 d3 49 83 c6 18 4c 89 f0 48 c1 e8 03 42 80 3c 20 00
RSP: 0018:ffffc9000337faa0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8880511e7014 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff8880511e700f
RBP: ffffc9000337fc08 R08: dffffc0000000000 R09: fffff520007a0282
R10: fffff520007a0282 R11: 1ffff920007a0281 R12: dffffc0000000000
R13: ffff8880511e7017 R14: ffff88807419f000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f12668cc000 CR3: 0000000078f6f000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: df 42 0f filds 0xf(%rdx)
3: b6 0c mov $0xc,%dh
5: 21 84 c9 0f 85 be 01 and %eax,0x1be850f(%rcx,%rcx,8)
c: 00 00 add %al,(%rax)
e: 49 83 c5 17 add $0x17,%r13
12: 4c 89 e9 mov %r13,%rcx
15: 48 c1 e9 03 shr $0x3,%rcx
19: 42 0f b6 0c 21 movzbl (%rcx,%r12,1),%ecx
1e: 84 c9 test %cl,%cl
20: 0f 85 d5 01 00 00 jne 0x1fb
26: 8b 0b mov (%rbx),%ecx
28: 31 d2 xor %edx,%edx
* 2a: 48 f7 f1 div %rcx <-- trapping instruction
2d: 48 89 d3 mov %rdx,%rbx
30: 49 83 c6 18 add $0x18,%r14
34: 4c 89 f0 mov %r14,%rax
37: 48 c1 e8 03 shr $0x3,%rax
3b: 42 80 3c 20 00 cmpb $0x0,(%rax,%r12,1)


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