ALSA: pcm: Check PCM state at xfern compat ioctl

BugLink: http://bugs.launchpad.net/bugs/1774173

commit f13876e2 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

sound/core/pcm_compat.c

@@ -426,6 +426,8 @@ 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;