[v5.15] divide error in comedi_inc_scan_progress (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3330a8d33e08 Linux 5.15.201
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12a7c202580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=d754c7b8e146c62520df
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b65fe19af112/disk-3330a8d3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/351948519a0d/vmlinux-3330a8d3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a3b3f8477595/bzImage-3330a8d3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d754c7...@syzkaller.appspotmail.com

divide error: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 11046 Comm: syz.5.2037 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:comedi_inc_scan_progress+0x19e/0x430 drivers/comedi/drivers.c:563
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 01 de f5 f9 48 bb 00 00 00
RSP: 0018:ffffc90000007c80 EFLAGS: 00010046
RAX: 0000000000000001 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff8880782c4200 R08: ffff8880782c4200 R09: 1ffff9200095f200
R10: dffffc0000000000 R11: fffff5200095f201 R12: ffff8880782c4288
R13: 0000000000000002 R14: 0000000000000000 R15: ffff8880782c4234
FS: 00007fd6dbd5d6c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c32cb3b CR3: 000000002b7de000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
comedi_buf_write_samples+0x371/0x5e0 drivers/comedi/comedi_buf.c:647
das16m1_handler+0x212/0x4b0 drivers/comedi/drivers/das16m1.c:414
das16m1_interrupt+0xa7/0x170 drivers/comedi/drivers/das16m1.c:471
__handle_irq_event_percpu+0x299/0x9d0 kernel/irq/handle.c:156
handle_irq_event_percpu kernel/irq/handle.c:196 [inline]
handle_irq_event+0xa5/0x220 kernel/irq/handle.c:213
handle_edge_irq+0x243/0xb20 kernel/irq/chip.c:819
generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
handle_irq arch/x86/kernel/irq.c:233 [inline]
__common_interrupt+0xd7/0x1e0 arch/x86/kernel/irq.c:252
common_interrupt+0xb0/0xd0 arch/x86/kernel/irq.c:242
</IRQ>
<TASK>
asm_common_interrupt+0x22/0x40 arch/x86/include/asm/idtentry.h:667
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:194
Code: c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f7 44 24 20 00 02 00 00 41 c6 04 07 f8 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 2f ca 8c f7 65 8b 05 d0 d7 3c 76 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc900032dfba0 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a06 RCX: 2708b44bb5e59700
RDX: dffffc0000000000 RSI: ffffffff8a2b2780 RDI: 0000000000000001
RBP: ffffc900032dfc30 R08: ffffffff901d3117 R09: 1ffffffff203a622
R10: dffffc0000000000 R11: fffffbfff203a623 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffffff966012c8 R15: 1ffff9200065bf74
spin_unlock_irqrestore include/linux/spinlock.h:419 [inline]
autoconfig drivers/tty/serial/8250/8250_port.c:1336 [inline]
serial8250_config_port+0x1bbf/0x38d0 drivers/tty/serial/8250/8250_port.c:3195
univ8250_config_port+0x3b1/0x960 drivers/tty/serial/8250/8250_core.c:446
uart_do_autoconfig drivers/tty/serial/serial_core.c:1164 [inline]
uart_ioctl+0x685/0x800 drivers/tty/serial/serial_core.c:1428
tty_ioctl+0x84c/0xc20 drivers/tty/tty_io.c:2810
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
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: 0033:0x7fd6ddb03799
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:00007fd6dbd5d028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fd6ddd7cfa0 RCX: 00007fd6ddb03799
RDX: 0000000000000000 RSI: 0000000000005453 RDI: 0000000000000003
RBP: 00007fd6ddb99bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd6ddd7d038 R14: 00007fd6ddd7cfa0 R15: 00007ffef1f28268
</TASK>
Modules linked in:
---[ end trace ad965918d4da6026 ]---
RIP: 0010:comedi_inc_scan_progress+0x19e/0x430 drivers/comedi/drivers.c:563
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 01 de f5 f9 48 bb 00 00 00
RSP: 0018:ffffc90000007c80 EFLAGS: 00010046
RAX: 0000000000000001 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff8880782c4200 R08: ffff8880782c4200 R09: 1ffff9200095f200
R10: dffffc0000000000 R11: fffff5200095f201 R12: ffff8880782c4288
R13: 0000000000000002 R14: 0000000000000000 R15: ffff8880782c4234
FS: 00007fd6dbd5d6c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c32cb3b CR3: 000000002b7de000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
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 01 de f5 f9 call 0xf9f5de3c
3b: 48 rex.W
3c: bb .byte 0xbb
3d: 00 00 add %al,(%rax)


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