[syzbot] KMSAN: uninit-value in snd_rawmidi_ioctl

[syzbot] KMSAN: uninit-value in snd_rawmidi_ioctl

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    8b936c96768e kmsan: core: remove the accidentally committe..
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=11791d89b00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e00a8959fdd3f3e8
dashboard link: https://syzkaller.appspot.com/bug?extid=88412ee8811832b00dbe
compiler:       clang version 14.0.0 (git@github.com:llvm/llvm-project.git 0996585c8e3b3d409494eb5f1cad714b9e1f7fb5), GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13a7abf9b00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=172410b9b00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+88412ee8811832b00dbe@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in snd_rawmidi_ioctl+0xf1e/0x1330 sound/core/rawmidi.c:887
 snd_rawmidi_ioctl+0xf1e/0x1330 sound/core/rawmidi.c:887
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0x2df/0x4a0 fs/ioctl.c:860
 __x64_sys_ioctl+0xd8/0x110 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Uninit was created at:
 slab_post_alloc_hook mm/slab.h:524 [inline]
 slab_alloc_node mm/slub.c:3251 [inline]
 slab_alloc mm/slub.c:3259 [inline]
 kmem_cache_alloc_trace+0xaca/0x1140 mm/slub.c:3276
 kmalloc include/linux/slab.h:590 [inline]
 snd_rawmidi_open+0x70d/0x1390 sound/core/rawmidi.c:445
 snd_open+0x702/0x890 sound/core/sound.c:169
 chrdev_open+0xbc9/0xd80 fs/char_dev.c:414
 do_dentry_open+0x1128/0x1bf0 fs/open.c:822
 vfs_open+0xaf/0xe0 fs/open.c:957
 do_open fs/namei.c:3426 [inline]
 path_openat+0x52f1/0x5dd0 fs/namei.c:3559
 do_filp_open+0x306/0x760 fs/namei.c:3586
 do_sys_openat2+0x263/0x8f0 fs/open.c:1212
 do_sys_open fs/open.c:1228 [inline]
 __do_sys_openat fs/open.c:1244 [inline]
 __se_sys_openat fs/open.c:1239 [inline]
 __x64_sys_openat+0x35f/0x3c0 fs/open.c:1239
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

CPU: 1 PID: 6368 Comm: syz-executor467 Not tainted 5.16.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
=====================================================


---
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Re: [syzbot] KMSAN: uninit-value in snd_rawmidi_ioctl

[Jaroslav Kysela]

On 18. 12. 21 12:17, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    8b936c96768e kmsan: core: remove the accidentally committe..
> git tree:       https://github.com/google/kmsan.git master
> console output: https://syzkaller.appspot.com/x/log.txt?x=11791d89b00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e00a8959fdd3f3e8
> dashboard link: https://syzkaller.appspot.com/bug?extid=88412ee8811832b00dbe
> compiler:       clang version 14.0.0 (git@github.com:llvm/llvm-project.git 0996585c8e3b3d409494eb5f1cad714b9e1f7fb5), GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13a7abf9b00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=172410b9b00000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+88412ee8811832b00dbe@syzkaller.appspotmail.com
> 
> =====================================================
> BUG: KMSAN: uninit-value in snd_rawmidi_ioctl+0xf1e/0x1330 sound/core/rawmidi.c:887
>   snd_rawmidi_ioctl+0xf1e/0x1330 sound/core/rawmidi.c:887

Nice catch. I wonder why the problem was not detected by tests. The patch 
bellow should initialize the user_pversion variable:

diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c
index 6f30231bdb88..befa9809ff00 100644
--- a/sound/core/rawmidi.c
+++ b/sound/core/rawmidi.c
@@ -447,6 +447,7 @@ static int snd_rawmidi_open(struct inode *inode, struct 
file *file)
                 err = -ENOMEM;
                 goto __error;
         }
+       rawmidi_file->user_pversion = 0;
         init_waitqueue_entry(&wait, current);
         add_wait_queue(&rmidi->open_wait, &wait);
         while (1) {

I'll send the path in the proper format ASAP.

					Jaroslav

-- 
Jaroslav Kysela <perex@perex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.