linux-kernel - Re: [syzbot] [comedi?] BUG: unable to handle kernel paging request in dt2815

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [day] [month] [year] [list]
Message-ID: <6976fd42.050a0220.226181.0012.GAE@google.com>
Date: Sun, 25 Jan 2026 21:36:02 -0800
From: syzbot <syzbot+72f94b474d6e50b71ffc@...kaller.appspotmail.com>
To: kartikey406@...il.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [comedi?] BUG: unable to handle kernel paging request in dt2815_attach

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: After second outb
dt2815: Loop iteration 1, dev->iobase = 0x7d
dt2815: status = 0xff
dt2815: About to do second outb, dev = ffff8880408c7000, 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 465c6067 P4D 465c6067 PUD 0 
Oops: Oops: 0002 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5846 Comm: syz.0.17 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+0x6a8/0x9e0 drivers/comedi/drivers/dt2815.c:210
Code: 8b 96 d0 01 00 00 48 c7 c7 e0 f7 8b 8c 4c 89 f6 e8 7d 5f f5 ff 43 80 3c 27 00 74 08 4c 89 ef e8 ce 02 f9 00 41 8b 55 00 ff c2 <31> 66 90 48 c7 c7 60 f8 8b 8c e8 59 5f f5 ff 83 fd 63 75 9c eb 71
RSP: 0018:ffffc90001987a80 EFLAGS: 00010206
RAX: 000000000000004b RBX: ffffc90001987bc0 RCX: fd82e65c6f5c7300
RDX: 000000000000007e RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffffc90001987807 R09: 1ffff92000330f00
R10: dffffc0000000000 R11: fffff52000330f01 R12: dffffc0000000000
R13: ffff8880408c71d0 R14: ffff8880408c7000 R15: 1ffff11008118e3a
FS:  00007f4b609056c0(0000) GS:ffff88808cf1b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000007fffff90 CR3: 00000000465ca000 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: 0033:0x7f4b5f99acb9
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:00007f4b60905028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f4b5fc15fa0 RCX: 00007f4b5f99acb9
RDX: 0000200000000080 RSI: 0000000040946400 RDI: 0000000000000003
RBP: 00007f4b5fa08bf7 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4b5fc16038 R14: 00007f4b5fc15fa0 R15: 00007ffc911b33b8
 </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+0x6a8/0x9e0 drivers/comedi/drivers/dt2815.c:210
Code: 8b 96 d0 01 00 00 48 c7 c7 e0 f7 8b 8c 4c 89 f6 e8 7d 5f f5 ff 43 80 3c 27 00 74 08 4c 89 ef e8 ce 02 f9 00 41 8b 55 00 ff c2 <31> 66 90 48 c7 c7 60 f8 8b 8c e8 59 5f f5 ff 83 fd 63 75 9c eb 71
RSP: 0018:ffffc90001987a80 EFLAGS: 00010206
RAX: 000000000000004b RBX: ffffc90001987bc0 RCX: fd82e65c6f5c7300
RDX: 000000000000007e RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffffc90001987807 R09: 1ffff92000330f00
R10: dffffc0000000000 R11: fffff52000330f01 R12: dffffc0000000000
R13: ffff8880408c71d0 R14: ffff8880408c7000 R15: 1ffff11008118e3a
FS:  00007f4b609056c0(0000) GS:ffff88808cf1b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000007fffff90 CR3: 00000000465ca000 CR4: 0000000000352ef0
----------------
Code disassembly (best guess):
   0:	8b 96 d0 01 00 00    	mov    0x1d0(%rsi),%edx
   6:	48 c7 c7 e0 f7 8b 8c 	mov    $0xffffffff8c8bf7e0,%rdi
   d:	4c 89 f6             	mov    %r14,%rsi
  10:	e8 7d 5f f5 ff       	call   0xfff55f92
  15:	43 80 3c 27 00       	cmpb   $0x0,(%r15,%r12,1)
  1a:	74 08                	je     0x24
  1c:	4c 89 ef             	mov    %r13,%rdi
  1f:	e8 ce 02 f9 00       	call   0xf902f2
  24:	41 8b 55 00          	mov    0x0(%r13),%edx
  28:	ff c2                	inc    %edx
* 2a:	31 66 90             	xor    %esp,-0x70(%rsi) <-- trapping instruction
  2d:	48 c7 c7 60 f8 8b 8c 	mov    $0xffffffff8c8bf860,%rdi
  34:	e8 59 5f f5 ff       	call   0xfff55f92
  39:	83 fd 63             	cmp    $0x63,%ebp
  3c:	75 9c                	jne    0xffffffda
  3e:	eb 71                	jmp    0xb1


Tested on:

commit:         63804fed Linux 6.19-rc7
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15ba3002580000
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=1214b9ac580000