On Wed, 02 May 2018 04:12:02 +0200, syzbot wrote:
Hello,
syzbot found the following crash on:
HEAD commit: fff75eb2a08c Merge tag 'errseq-v4.17' of git://git.kernel.o... git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?id=6530078334779392 kernel config: https://syzkaller.appspot.com/x/.config?id=6493557782959164711 dashboard link: https://syzkaller.appspot.com/bug?extid=1dac3a4f6bc9c1c675d4 compiler: gcc (GCC) 8.0.1 20180413 (experimental) userspace arch: i386 syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?id=5691583680741376
IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+1dac3a4f6bc9c1c675d4@syzkaller.appspotmail.com
random: sshd: uninitialized urandom read (32 bytes read) random: sshd: uninitialized urandom read (32 bytes read) random: sshd: uninitialized urandom read (32 bytes read) random: sshd: uninitialized urandom read (32 bytes read) IPVS: ftp: loaded support on port[0] = 21 WARNING: CPU: 1 PID: 4520 at sound/core/pcm_lib.c:2057 pcm_sanity_check sound/core/pcm_lib.c:2057 [inline]
...
snd_pcm_ioctl_compat+0xc96/0x1c90 sound/core/pcm_compat.c:716
OK, this is an easy one, just a forgotten PCM state check. The patch below should fix it.
thanks,
Takashi
-- 8< -- From: Takashi Iwai tiwai@suse.de Subject: [PATCH] ALSA: pcm: Check PCM state at xfern compat ioctl
Since snd_pcm_ioctl_xfern_compat() has no PCM state check, it may go further and hit the sanity check pcm_sanity_check() when the ioctl is called right after open. It may eventually spew a kernel warning, as triggered by syzbot, depending on kconfig.
The lack of PCM state check there was just an oversight. Although it's no real crash, the spurious kernel warning is annoying, so let's add the proper check.
Reported-by: syzbot+1dac3a4f6bc9c1c675d4@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de --- sound/core/pcm_compat.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/sound/core/pcm_compat.c b/sound/core/pcm_compat.c index 06d7c40af570..6491afbb5fd5 100644 --- a/sound/core/pcm_compat.c +++ b/sound/core/pcm_compat.c @@ -423,6 +423,8 @@ static int snd_pcm_ioctl_xfern_compat(struct snd_pcm_substream *substream, return -ENOTTY; if (substream->stream != dir) return -EINVAL; + if (substream->runtime->status->state == SNDRV_PCM_STATE_OPEN) + return -EBADFD;
if ((ch = substream->runtime->channels) > 128) return -EINVAL;