UBSAN: shift-out-of-bounds in pcl726_attach

Status: fixed on 2025/10/06 10:09
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+454978c387d406752b7c@syzkaller.appspotmail.com
Fix commit: 96cb948408b3 comedi: pcl726: Prevent invalid irq number
First crash: 367d, last: 339d
Fix bisection: fixed by (bisect log) :
commit 0eb4ed2aa261dee228f1668dbfa6d87353e8162d
Author: Edward Adam Davis <eadavis@qq.com>
Date: Mon Jul 7 12:39:58 2025 +0000

  comedi: pcl726: Prevent invalid irq number

  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/08/01 upstream (ToT) 89748acdf226 C [report] UBSAN: shift-out-of-bounds in pcl726_attach
2025/09/18 upstream (ToT) 992d4e481e95 C Didn't crash
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 UBSAN: shift-out-of-bounds in pcl726_attach origin:upstream -1 syz, C done 19 339d 390d 2/3 upstream: reported C repro on 2025/07/08 03:45
linux-6.1 UBSAN: shift-out-of-bounds in pcl726_attach -1 syz, C done 16 339d 367d 3/3 fixed on 2025/10/06 10:35
upstream UBSAN: shift-out-of-bounds in pcl726_attach comedi -1 syz, C 318 344d 393d 29/29 fixed on 2025/10/09 01:15

Sample crash report:
================================================================================
UBSAN: shift-out-of-bounds in drivers/comedi/drivers/pcl726.c:331:46
shift exponent -4 is negative
CPU: 1 PID: 5918 Comm: syz.3.15 Not tainted 6.6.102-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 ubsan_epilogue+0xa/0x30 lib/ubsan.c:217
 __ubsan_handle_shift_out_of_bounds+0x380/0x400 lib/ubsan.c:387
 pcl726_attach+0xab9/0xd40 drivers/comedi/drivers/pcl726.c:331
 comedi_device_attach+0x519/0x660 drivers/comedi/drivers.c:998
 do_devconfig_ioctl drivers/comedi/comedi_fops.c:855 [inline]
 comedi_unlocked_ioctl+0x68d/0xf90 drivers/comedi/comedi_fops.c:2156
 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: 0033:0x7fb834f8ebe9
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:00007fb835e45038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fb8351b5fa0 RCX: 00007fb834f8ebe9
RDX: 00002000000005c0 RSI: 0000000040946400 RDI: 0000000000000003
RBP: 00007fb835011e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb8351b6038 R14: 00007fb8351b5fa0 R15: 00007fff3d25c3e8
 </TASK>
================================================================================

Crashes (17):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/08/28 02:46 linux-6.6.y bb9c90ab9c5a e12e5ba4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/08/28 02:46 linux-6.6.y bb9c90ab9c5a e12e5ba4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/08/26 08:50 linux-6.6.y bb9c90ab9c5a bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/08/26 08:49 linux-6.6.y bb9c90ab9c5a bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/08/23 06:50 linux-6.6.y bb9c90ab9c5a bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/08/23 06:47 linux-6.6.y bb9c90ab9c5a bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/08/19 09:51 linux-6.6.y bb9c90ab9c5a 523f460e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/08/19 09:51 linux-6.6.y bb9c90ab9c5a 523f460e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/08/16 19:00 linux-6.6.y bb9c90ab9c5a 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/08/16 18:59 linux-6.6.y bb9c90ab9c5a 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/08/06 10:45 linux-6.6.y 3a8ababb8b6a ffe1dd46 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/08/06 10:44 linux-6.6.y 3a8ababb8b6a ffe1dd46 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/08/06 10:35 linux-6.6.y 3a8ababb8b6a ffe1dd46 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/08/06 10:34 linux-6.6.y 3a8ababb8b6a ffe1dd46 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/07/31 14:48 linux-6.6.y dbcb8d8e4163 f8f2b4da .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/07/31 14:19 linux-6.6.y dbcb8d8e4163 f8f2b4da .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
2025/07/31 14:15 linux-6.6.y dbcb8d8e4163 f8f2b4da .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan UBSAN: shift-out-of-bounds in pcl726_attach
* Struck through repros no longer work on HEAD.