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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+1dac3a4f6bc9c1c675d4@syzkaller.appspotmail.com,
        Takashi Iwai <tiwai@suse.de>
Subject: [PATCH 4.4 12/56] ALSA: pcm: Check PCM state at xfern compat ioctl
Date:   Mon, 14 May 2018 08:48:17 +0200
Message-Id: <20180514064756.256536571@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@suse.de>

commit f13876e2c33a657a71bcbb10f767c0951b165020 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>

---
 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;