linux-kernel - Re: [syzbot] [comedi?] KMSAN: kernel-infoleak in do_insnlist

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Message-ID: <688b1b62.a00a0220.26d0e1.0039.GAE@google.com>
Date: Thu, 31 Jul 2025 00:29:38 -0700
From: syzbot <syzbot+fb4362a104d45ab09cf9@...kaller.appspotmail.com>
To: abbotti@....co.uk, hsweeten@...ionengravers.com, 
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [comedi?] KMSAN: kernel-infoleak in do_insnlist_ioctl

syzbot has found a reproducer for the following issue on:

HEAD commit:    e8d780dcd957 Merge tag 'slab-for-6.17' of git://git.kernel..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=154b8f82580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=30a934bba3cd727
dashboard link: https://syzkaller.appspot.com/bug?extid=fb4362a104d45ab09cf9
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10a04ca2580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13a269bc580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f57c48189b63/disk-e8d780dc.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5b7ee73a2a25/vmlinux-e8d780dc.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e48af4e6a5c3/bzImage-e8d780dc.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fb4362a104d45ab09cf9@...kaller.appspotmail.com

comedi comedi3: 8255: I/O port conflict (0x2,4)
comedi comedi3: 8255: I/O port conflict (0x10000,4)
comedi comedi3: 8255: I/O port conflict (0x4,4)
comedi comedi3: 8255: I/O port conflict (0x4,4)
=====================================================
BUG: KMSAN: kernel-infoleak-after-free in instrument_copy_to_user include/linux/instrumented.h:114 [inline]
BUG: KMSAN: kernel-infoleak-after-free in _inline_copy_to_user include/linux/uaccess.h:196 [inline]
BUG: KMSAN: kernel-infoleak-after-free in _copy_to_user+0xcc/0x120 lib/usercopy.c:26
 instrument_copy_to_user include/linux/instrumented.h:114 [inline]
 _inline_copy_to_user include/linux/uaccess.h:196 [inline]
 _copy_to_user+0xcc/0x120 lib/usercopy.c:26
 copy_to_user include/linux/uaccess.h:225 [inline]
 do_insnlist_ioctl+0x66e/0x930 drivers/comedi/comedi_fops.c:1595
 comedi_unlocked_ioctl+0x1e78/0x1f60 drivers/comedi/comedi_fops.c:2293
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:598 [inline]
 __se_sys_ioctl+0x239/0x400 fs/ioctl.c:584
 __x64_sys_ioctl+0x97/0xe0 fs/ioctl.c:584
 x64_sys_call+0x1cbc/0x3e20 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 slab_free_hook mm/slub.c:2342 [inline]
 slab_free mm/slub.c:4679 [inline]
 kfree+0x252/0xec0 mm/slub.c:4878
 tomoyo_supervisor+0xc57/0x3100 security/tomoyo/common.c:2250
 tomoyo_audit_path_number_log security/tomoyo/file.c:235 [inline]
 tomoyo_path_number_perm+0x4d8/0x7d0 security/tomoyo/file.c:734
 tomoyo_file_ioctl+0x3d/0x50 security/tomoyo/tomoyo.c:350
 security_file_ioctl+0x141/0x590 security/security.c:2943
 __do_sys_ioctl fs/ioctl.c:592 [inline]
 __se_sys_ioctl+0xbb/0x400 fs/ioctl.c:584
 __x64_sys_ioctl+0x97/0xe0 fs/ioctl.c:584
 x64_sys_call+0x1cbc/0x3e20 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Bytes 4-583 of 584 are uninitialized
Memory access of size 584 starts at ffff88814448f800

CPU: 1 UID: 0 PID: 5809 Comm: syz-executor572 Not tainted 6.16.0-syzkaller-06699-ge8d780dcd957 #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
=====================================================


---
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#syz test: git://repo/address.git branch-or-commit-hash
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