linux-kernel - [PATCH 4.9 21/96] ALSA: aloop: Release cable upon open error path

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Message-Id: <20180115123406.311145651@linuxfoundation.org>
Date:   Mon, 15 Jan 2018 13:34:20 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Takashi Iwai <tiwai@...e.de>
Subject: [PATCH 4.9 21/96] ALSA: aloop: Release cable upon open error path

4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Takashi Iwai <tiwai@...e.de>

commit 9685347aa0a5c2869058ca6ab79fd8e93084a67f upstream.

The aloop runtime object and its assignment in the cable are left even
when opening a substream fails.  This doesn't mean any memory leak,
but it still keeps the invalid pointer that may be referred by the
another side of the cable spontaneously, which is a potential Oops
cause.

Clean up the cable assignment and the empty cable upon the error path
properly.

Fixes: 597603d615d2 ("ALSA: introduce the snd-aloop module for the PCM loopback")
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 sound/drivers/aloop.c |   38 +++++++++++++++++++++++++-------------
 1 file changed, 25 insertions(+), 13 deletions(-)

--- a/sound/drivers/aloop.c
+++ b/sound/drivers/aloop.c
@@ -658,12 +658,31 @@ static int rule_channels(struct snd_pcm_
 	return snd_interval_refine(hw_param_interval(params, rule->var), &t);
 }
 
+static void free_cable(struct snd_pcm_substream *substream)
+{
+	struct loopback *loopback = substream->private_data;
+	int dev = get_cable_index(substream);
+	struct loopback_cable *cable;
+
+	cable = loopback->cables[substream->number][dev];
+	if (!cable)
+		return;
+	if (cable->streams[!substream->stream]) {
+		/* other stream is still alive */
+		cable->streams[substream->stream] = NULL;
+	} else {
+		/* free the cable */
+		loopback->cables[substream->number][dev] = NULL;
+		kfree(cable);
+	}
+}
+
 static int loopback_open(struct snd_pcm_substream *substream)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct loopback *loopback = substream->private_data;
 	struct loopback_pcm *dpcm;
-	struct loopback_cable *cable;
+	struct loopback_cable *cable = NULL;
 	int err = 0;
 	int dev = get_cable_index(substream);
 
@@ -682,7 +701,6 @@ static int loopback_open(struct snd_pcm_
 	if (!cable) {
 		cable = kzalloc(sizeof(*cable), GFP_KERNEL);
 		if (!cable) {
-			kfree(dpcm);
 			err = -ENOMEM;
 			goto unlock;
 		}
@@ -724,6 +742,10 @@ static int loopback_open(struct snd_pcm_
 	else
 		runtime->hw = cable->hw;
  unlock:
+	if (err < 0) {
+		free_cable(substream);
+		kfree(dpcm);
+	}
 	mutex_unlock(&loopback->cable_lock);
 	return err;
 }
@@ -732,20 +754,10 @@ static int loopback_close(struct snd_pcm
 {
 	struct loopback *loopback = substream->private_data;
 	struct loopback_pcm *dpcm = substream->runtime->private_data;
-	struct loopback_cable *cable;
-	int dev = get_cable_index(substream);
 
 	loopback_timer_stop(dpcm);
 	mutex_lock(&loopback->cable_lock);
-	cable = loopback->cables[substream->number][dev];
-	if (cable->streams[!substream->stream]) {
-		/* other stream is still alive */
-		cable->streams[substream->stream] = NULL;
-	} else {
-		/* free the cable */
-		loopback->cables[substream->number][dev] = NULL;
-		kfree(cable);
-	}
+	free_cable(substream);
 	mutex_unlock(&loopback->cable_lock);
 	return 0;
 }