divide error in comedi_buf_write

Kernel	Title	Rank 🛈	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	divide error in comedi_buf_write_free kernel	2				3	10d	10d	0/29	upstream: reported on 2025/07/09 17:38
divide error: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 9356 Comm: syz.1.1703 Not tainted 5.15.186-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:comedi_buf_munge drivers/comedi/comedi_buf.c:398 [inline]
RIP: 0010:comedi_buf_write_free+0x3ae/0x7e0 drivers/comedi/comedi_buf.c:441
Code: 8c 24 80 00 00 00 42 0f b6 0c 39 84 c9 8b 5c 24 1c 4c 8b ac 24 a0 00 00 00 48 8b 34 24 0f 85 04 01 00 00 31 d2 48 8b 4c 24 48 <f7> 31 41 89 14 24 48 8b 44 24 78 42 0f b6 04 38 84 c0 48 8b 6c 24
RSP: 0018:ffffc90000007bd8 EFLAGS: 00010046
RAX: 0000000000000001 RBX: 0000000000000002 RCX: ffff88801e9dc088
RDX: 0000000000000000 RSI: ffff88801e9dc048 RDI: ffffc9000594a000
RBP: dffffc0000000000 R08: 0000000000000000 R09: fffff52000b29401
R10: fffff52000b29401 R11: 1ffff92000b29400 R12: ffff88801e9dc040
R13: ffff88801e9dc008 R14: 0000000000000002 R15: dffffc0000000000
FS:  00007f20b617d6c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b3141cff8 CR3: 000000001f5fb000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 comedi_buf_write_samples+0x366/0x5e0 drivers/comedi/comedi_buf.c:646
 das16m1_handler+0x212/0x4b0 drivers/comedi/drivers/das16m1.c:414
 das16m1_interrupt+0xa7/0x170 drivers/comedi/drivers/das16m1.c:471
 __handle_irq_event_percpu+0x291/0x9b0 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:lock_is_held_type+0x13a/0x190 kernel/locking/lockdep.c:5671
Code: 75 40 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 75 46 41 f7 c5 00 02 00 00 74 01 fb 65 48 8b 04 25 28 00 00 00 <48> 3b 44 24 08 75 3c 89 e8 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f
RSP: 0018:ffffc9000337fb38 EFLAGS: 00000206
RAX: 7f8c4ec0b82b3500 RBX: ffff888029f83b80 RCX: 7f8c4ec0b82b3500
RDX: 0000000000000000 RSI: ffffffff8a0b2460 RDI: ffffffff8a59ab80
RBP: 0000000000000000 R08: dffffc0000000000 R09: fffffbfff1ad2f76
R10: fffffbfff1ad2f76 R11: 1ffffffff1ad2f75 R12: dffffc0000000000
R13: 0000000000000246 R14: ffffffff8c11c000 R15: 00000000ffffffff
 lock_is_held include/linux/lockdep.h:287 [inline]
 ___might_sleep+0xa3/0x600 kernel/sched/core.c:9605
 do_recvmmsg+0x51f/0x7a0 net/socket.c:2825
 __sys_recvmmsg net/socket.c:2870 [inline]
 __do_sys_recvmmsg net/socket.c:2893 [inline]
 __se_sys_recvmmsg net/socket.c:2886 [inline]
 __x64_sys_recvmmsg+0x18d/0x240 net/socket.c:2886
 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: 0033:0x7f20b8336929
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:00007f20b617d038 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007f20b855e080 RCX: 00007f20b8336929
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000003
RBP: 00007f20b83b8b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f20b855e080 R15: 00007ffdc2ce3048
 </TASK>
Modules linked in:
---[ end trace e270f9e2b4152189 ]---
RIP: 0010:comedi_buf_munge drivers/comedi/comedi_buf.c:398 [inline]
RIP: 0010:comedi_buf_write_free+0x3ae/0x7e0 drivers/comedi/comedi_buf.c:441
Code: 8c 24 80 00 00 00 42 0f b6 0c 39 84 c9 8b 5c 24 1c 4c 8b ac 24 a0 00 00 00 48 8b 34 24 0f 85 04 01 00 00 31 d2 48 8b 4c 24 48 <f7> 31 41 89 14 24 48 8b 44 24 78 42 0f b6 04 38 84 c0 48 8b 6c 24
RSP: 0018:ffffc90000007bd8 EFLAGS: 00010046
RAX: 0000000000000001 RBX: 0000000000000002 RCX: ffff88801e9dc088
RDX: 0000000000000000 RSI: ffff88801e9dc048 RDI: ffffc9000594a000
RBP: dffffc0000000000 R08: 0000000000000000 R09: fffff52000b29401
R10: fffff52000b29401 R11: 1ffff92000b29400 R12: ffff88801e9dc040
R13: ffff88801e9dc008 R14: 0000000000000002 R15: dffffc0000000000
FS:  00007f20b617d6c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b3141cff8 CR3: 000000001f5fb000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	8c 24 80             	mov    %fs,(%rax,%rax,4)
   3:	00 00                	add    %al,(%rax)
   5:	00 42 0f             	add    %al,0xf(%rdx)
   8:	b6 0c                	mov    $0xc,%dh
   a:	39 84 c9 8b 5c 24 1c 	cmp    %eax,0x1c245c8b(%rcx,%rcx,8)
  11:	4c 8b ac 24 a0 00 00 	mov    0xa0(%rsp),%r13
  18:	00
  19:	48 8b 34 24          	mov    (%rsp),%rsi
  1d:	0f 85 04 01 00 00    	jne    0x127
  23:	31 d2                	xor    %edx,%edx
  25:	48 8b 4c 24 48       	mov    0x48(%rsp),%rcx
* 2a:	f7 31                	divl   (%rcx) <-- trapping instruction
  2c:	41 89 14 24          	mov    %edx,(%r12)
  30:	48 8b 44 24 78       	mov    0x78(%rsp),%rax
  35:	42 0f b6 04 38       	movzbl (%rax,%r15,1),%eax
  3a:	84 c0                	test   %al,%al
  3c:	48                   	rex.W
  3d:	8b                   	.byte 0x8b
  3e:	6c                   	insb   (%dx),%es:(%rdi)
  3f:	24                   	.byte 0x24