Re: [syzbot] [comedi?] BUG: unable to handle kernel paging request in dt2815_attach

[syzbot <syzbot+72f94b474d6e50b71ffc@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
BUG: unable to handle kernel paging request in dt2815_attach

dt2815: [PID 5821] ENTER dt2815_attach, it->options[0] = 0x7d
dt2815: [PID 5821] after comedi_request_region, dev->iobase = 0x7d
dt2815: [PID 5821] About to do FIRST outb, dev = ffff888040506800, dev->iobase = 0x7d
BUG: unable to handle page fault for address: 000000007fffff90
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 57fb4067 P4D 57fb4067 PUD 0 
Oops: Oops: 0002 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5821 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:__outb arch/x86/include/asm/shared/io.h:22 [inline]
RIP: 0010:dt2815_attach+0x6e0/0x1110 drivers/comedi/drivers/dt2815.c:187
Code: f5 ff 48 bd 00 00 00 00 00 fc ff df 41 80 3c 2c 00 74 12 4c 89 f7 e8 9f 02 f9 00 48 bd 00 00 00 00 00 fc ff df 41 8b 16 ff c2 <31> 66 90 41 0f b6 44 2d 00 84 c0 0f 85 00 08 00 00 8b 33 48 c7 c7
RSP: 0018:ffffc90002a8fa78 EFLAGS: 00010206
RAX: 0000000000000055 RBX: ffff88803405cf98 RCX: c9cdd809989aea00
RDX: 000000000000007e RSI: 0000000080000000 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffff88801fc247d3 R09: 1ffff11003f848fa
R10: dffffc0000000000 R11: ffffed1003f848fb R12: 1ffff110080a0d3a
R13: 1ffff1100680b9f3 R14: ffff8880405069d0 R15: ffff888040506800
FS:  00007f8323dfe6c0(0000) GS:ffff88808cf1b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000007fffff90 CR3: 0000000057ff9000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 comedi_device_attach+0x51f/0x720 drivers/comedi/drivers.c:1069
 do_devconfig_ioctl drivers/comedi/comedi_fops.c:928 [inline]
 comedi_unlocked_ioctl+0x701/0x1240 drivers/comedi/comedi_fops.c:2240
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f832479acb9
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:00007f8323dfe028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f8324a15fa0 RCX: 00007f832479acb9
RDX: 0000200000000080 RSI: 0000000040946400 RDI: 0000000000000003
RBP: 00007f8324808bf7 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8324a16038 R14: 00007f8324a15fa0 R15: 00007fff45a7cad8
 </TASK>
Modules linked in:
CR2: 000000007fffff90
---[ end trace 0000000000000000 ]---
RIP: 0010:__outb arch/x86/include/asm/shared/io.h:22 [inline]
RIP: 0010:dt2815_attach+0x6e0/0x1110 drivers/comedi/drivers/dt2815.c:187
Code: f5 ff 48 bd 00 00 00 00 00 fc ff df 41 80 3c 2c 00 74 12 4c 89 f7 e8 9f 02 f9 00 48 bd 00 00 00 00 00 fc ff df 41 8b 16 ff c2 <31> 66 90 41 0f b6 44 2d 00 84 c0 0f 85 00 08 00 00 8b 33 48 c7 c7
RSP: 0018:ffffc90002a8fa78 EFLAGS: 00010206
RAX: 0000000000000055 RBX: ffff88803405cf98 RCX: c9cdd809989aea00
RDX: 000000000000007e RSI: 0000000080000000 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffff88801fc247d3 R09: 1ffff11003f848fa
R10: dffffc0000000000 R11: ffffed1003f848fb R12: 1ffff110080a0d3a
R13: 1ffff1100680b9f3 R14: ffff8880405069d0 R15: ffff888040506800
FS:  00007f8323dfe6c0(0000) GS:ffff88808cf1b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000007fffff90 CR3: 0000000057ff9000 CR4: 0000000000352ef0
----------------
Code disassembly (best guess):
   0:	f5                   	cmc
   1:	ff 48 bd             	decl   -0x43(%rax)
   4:	00 00                	add    %al,(%rax)
   6:	00 00                	add    %al,(%rax)
   8:	00 fc                	add    %bh,%ah
   a:	ff                   	lcall  (bad)
   b:	df 41 80             	filds  -0x80(%rcx)
   e:	3c 2c                	cmp    $0x2c,%al
  10:	00 74 12 4c          	add    %dh,0x4c(%rdx,%rdx,1)
  14:	89 f7                	mov    %esi,%edi
  16:	e8 9f 02 f9 00       	call   0xf902ba
  1b:	48 bd 00 00 00 00 00 	movabs $0xdffffc0000000000,%rbp
  22:	fc ff df
  25:	41 8b 16             	mov    (%r14),%edx
  28:	ff c2                	inc    %edx
* 2a:	31 66 90             	xor    %esp,-0x70(%rsi) <-- trapping instruction
  2d:	41 0f b6 44 2d 00    	movzbl 0x0(%r13,%rbp,1),%eax
  33:	84 c0                	test   %al,%al
  35:	0f 85 00 08 00 00    	jne    0x83b
  3b:	8b 33                	mov    (%rbx),%esi
  3d:	48                   	rex.W
  3e:	c7                   	.byte 0xc7
  3f:	c7                   	.byte 0xc7


Tested on:

commit:         63804fed Linux 6.19-rc7
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12d6905a580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e2e5d7c9c1e01cf4
dashboard link: https://syzkaller.appspot.com/bug?extid=72f94b474d6e50b71ffc
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=16a40a44580000