linux-kernel - [syzbot] [kernel?] KMSAN: kernel-infoleak in do_insn

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Message-ID: <68794b99.a70a0220.693ce.0053.GAE@google.com>
Date: Thu, 17 Jul 2025 12:14:33 -0700
From: syzbot <syzbot+a5e45f768aab5892da5d@...kaller.appspotmail.com>
To: abbotti@....co.uk, hsweeten@...ionengravers.com, 
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [kernel?] KMSAN: kernel-infoleak in do_insn_ioctl

Hello,

syzbot found the following issue on:

HEAD commit:    e2291551827f Merge tag 'probes-fixes-v6.16-rc6' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1220e7d4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fdecd0cbf7c2893
dashboard link: https://syzkaller.appspot.com/bug?extid=a5e45f768aab5892da5d
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/45d0dd363fc0/disk-e2291551.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2ac861991e19/vmlinux-e2291551.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a6c77d2eaafd/bzImage-e2291551.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a5e45f768aab5892da5d@...kaller.appspotmail.com

=====================================================
BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline]
BUG: KMSAN: kernel-infoleak in _inline_copy_to_user include/linux/uaccess.h:196 [inline]
BUG: KMSAN: kernel-infoleak 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_insn_ioctl+0x516/0x630 drivers/comedi/comedi_fops.c:1641
 comedi_unlocked_ioctl+0x13dd/0x1e00 drivers/comedi/comedi_fops.c:2263
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0x239/0x400 fs/ioctl.c:893
 __x64_sys_ioctl+0x97/0xe0 fs/ioctl.c:893
 x64_sys_call+0x1ebe/0x3db0 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_post_alloc_hook mm/slub.c:4154 [inline]
 slab_alloc_node mm/slub.c:4197 [inline]
 __do_kmalloc_node mm/slub.c:4327 [inline]
 __kmalloc_noprof+0x95f/0x1310 mm/slub.c:4340
 kmalloc_noprof include/linux/slab.h:909 [inline]
 kmalloc_array_noprof include/linux/slab.h:948 [inline]
 do_insn_ioctl+0x108/0x630 drivers/comedi/comedi_fops.c:1623
 comedi_unlocked_ioctl+0x13dd/0x1e00 drivers/comedi/comedi_fops.c:2263
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0x239/0x400 fs/ioctl.c:893
 __x64_sys_ioctl+0x97/0xe0 fs/ioctl.c:893
 x64_sys_call+0x1ebe/0x3db0 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 ffff88810355d000

CPU: 0 UID: 0 PID: 12350 Comm: syz.1.1721 Tainted: G        W           6.16.0-rc6-syzkaller-00037-ge2291551827f #0 PREEMPT(none) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
=====================================================


---
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