linux-kernel - Re: [syzbot] KMSAN: uninit-value in snd_rawmidi

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Message-ID: <9603b40e-d038-1252-d613-8ece55029f07@perex.cz>
Date:   Sat, 18 Dec 2021 13:29:43 +0100
From:   Jaroslav Kysela <perex@...ex.cz>
To:     syzbot <syzbot+88412ee8811832b00dbe@...kaller.appspotmail.com>,
        alsa-devel@...a-project.org, broonie@...nel.org, coding@...ic.se,
        colin.king@...el.com, glider@...gle.com, joe@...ches.com,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        tiwai@...e.com
Subject: Re: [syzbot] KMSAN: uninit-value in snd_rawmidi_ioctl

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@...hub.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@...kaller.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@...ex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.