From f13876e2c33a657a71bcbb10f767c0951b165020 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Wed, 2 May 2018 08:48:46 +0200
Subject: [PATCH] ALSA: pcm: Check PCM state at xfern compat ioctl
Git-commit: f13876e2c33a657a71bcbb10f767c0951b165020
Patch-mainline: v4.17-rc4
References: bsc#1051510

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(+)

--- a/sound/core/pcm_compat.c
+++ b/sound/core/pcm_compat.c
@@ -426,6 +426,8 @@ static int snd_pcm_ioctl_xfern_compat(st
 		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;