[v6.6] divide error in comedi_inc_scan_progress

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d96eb99e2f0e Linux 6.6.99
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13a124f0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=bfd82343ac39d3b
dashboard link: https://syzkaller.appspot.com/bug?extid=4158da92d6b01e6e7f64
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/11b332f11d00/disk-d96eb99e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8a063193b98f/vmlinux-d96eb99e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b36214b822e5/bzImage-d96eb99e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4158da...@syzkaller.appspotmail.com

divide error: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 469 Comm: syz.7.7009 Not tainted 6.6.99-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:comedi_inc_scan_progress+0x1a2/0x430 drivers/comedi/drivers.c:555
Code: b6 0c 19 84 c9 0f 85 b8 01 00 00 03 45 34 4c 8d a5 88 00 00 00 4c 89 e1 48 c1 e9 03 0f b6 0c 19 84 c9 0f 85 c7 01 00 00 31 d2 <41> f7 34 24 41 89 17 45 89 ec eb 0f e8 8d f6 8b f9 48 bb 00 00 00
RSP: 0018:ffffc90000007c88 EFLAGS: 00010046
RAX: 0000000000000001 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff888067812800 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffff520023aa001 R12: ffff888067812888
R13: 0000000000000002 R14: 0000000000000000 R15: ffff888067812834
FS: 00007f83585836c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b32e13ff8 CR3: 0000000078b05000 CR4: 00000000003506f0
Call Trace:
<IRQ>
comedi_buf_write_samples+0x372/0x5d0 drivers/comedi/comedi_buf.c:646
parport_interrupt+0xf4/0x150 drivers/comedi/drivers/comedi_parport.c:218
__handle_irq_event_percpu+0x276/0x930 kernel/irq/handle.c:158
handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:210
handle_edge_irq+0x247/0xb30 kernel/irq/chip.c:831
generic_handle_irq_desc include/linux/irqdesc.h:161 [inline]
handle_irq arch/x86/kernel/irq.c:240 [inline]
__common_interrupt+0x13b/0x230 arch/x86/kernel/irq.c:259
common_interrupt+0xb4/0xd0 arch/x86/kernel/irq.c:249
</IRQ>
<TASK>
asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:678
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xa9/0x110 kernel/locking/spinlock.c:194
Code: 74 05 e8 6a 38 15 f7 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> e2 b2 e4 f6 65 8b 05 f3 f8 8c 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc9000c387a40 EFLAGS: 00000206
RAX: 0521c3dae291d300 RBX: 0000000000000a06 RCX: 0521c3dae291d300
RDX: dffffc0000000000 RSI: ffffffff8aaaba40 RDI: 0000000000000001
RBP: ffffc9000c387ad0 R08: ffffffff90da2577 R09: 1ffffffff21b44ae
R10: dffffc0000000000 R11: fffffbfff21b44af R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffffff971d2ce0 R15: 1ffff92001870f48
spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
autoconfig drivers/tty/serial/8250/8250_port.c:1307 [inline]
serial8250_config_port+0x2697/0x39c0 drivers/tty/serial/8250/8250_port.c:3222
univ8250_config_port+0x3b5/0x960 drivers/tty/serial/8250/8250_core.c:445
uart_do_autoconfig drivers/tty/serial/serial_core.c:1204 [inline]
uart_ioctl+0xddf/0xfb0 drivers/tty/serial/serial_core.c:1603
tty_ioctl+0x926/0xdd0 drivers/tty/tty_io.c:2779
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f835778e9a9
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:00007f8358583038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f83579b6080 RCX: 00007f835778e9a9
RDX: 0000000000000000 RSI: 0000000000005453 RDI: 0000000000000009
RBP: 00007f8357810d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f83579b6080 R15: 00007ffcddf50c08
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:comedi_inc_scan_progress+0x1a2/0x430 drivers/comedi/drivers.c:555
Code: b6 0c 19 84 c9 0f 85 b8 01 00 00 03 45 34 4c 8d a5 88 00 00 00 4c 89 e1 48 c1 e9 03 0f b6 0c 19 84 c9 0f 85 c7 01 00 00 31 d2 <41> f7 34 24 41 89 17 45 89 ec eb 0f e8 8d f6 8b f9 48 bb 00 00 00
RSP: 0018:ffffc90000007c88 EFLAGS: 00010046
RAX: 0000000000000001 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff888067812800 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffff520023aa001 R12: ffff888067812888
R13: 0000000000000002 R14: 0000000000000000 R15: ffff888067812834
FS: 00007f83585836c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b32e13ff8 CR3: 0000000078b05000 CR4: 00000000003506f0
----------------
Code disassembly (best guess):
0: b6 0c mov $0xc,%dh
2: 19 84 c9 0f 85 b8 01 sbb %eax,0x1b8850f(%rcx,%rcx,8)
9: 00 00 add %al,(%rax)
b: 03 45 34 add 0x34(%rbp),%eax
e: 4c 8d a5 88 00 00 00 lea 0x88(%rbp),%r12
15: 4c 89 e1 mov %r12,%rcx
18: 48 c1 e9 03 shr $0x3,%rcx
1c: 0f b6 0c 19 movzbl (%rcx,%rbx,1),%ecx
20: 84 c9 test %cl,%cl
22: 0f 85 c7 01 00 00 jne 0x1ef
28: 31 d2 xor %edx,%edx
* 2a: 41 f7 34 24 divl (%r12) <-- trapping instruction
2e: 41 89 17 mov %edx,(%r15)
31: 45 89 ec mov %r13d,%r12d
34: eb 0f jmp 0x45
36: e8 8d f6 8b f9 call 0xf98bf6c8
3b: 48 rex.W
3c: bb .byte 0xbb
3d: 00 00 add %al,(%rax)


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.