sound: Fix esoteric double free in the dummy sound driver.

The dummy driver uses runtime->private_free but still frees its pcm structures on error paths. This is esoteric because the error paths in question are unreachable. Thus the bug is only a problem when someone copies this code into other drivers. Signed-off-by: Daniel R Thompson <[email protected]> Signed-off-by: Jaroslav Kysela <[email protected]>
mrcsosa · Aug 15, 2008 · 54e8e21 · 54e8e21
1 parent 8daaaa9
commit 54e8e21
Showing 1 changed file with 4 additions and 6 deletions.
diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c
@@ -354,6 +354,7 @@ static int snd_card_dummy_playback_open(struct snd_pcm_substream *substream)
 	if ((dpcm = new_pcm_stream(substream)) == NULL)
 		return -ENOMEM;
 	runtime->private_data = dpcm;
+	/* makes the infrastructure responsible for freeing dpcm */
 	runtime->private_free = snd_card_dummy_runtime_free;
 	runtime->hw = snd_card_dummy_playback;
 	if (substream->pcm->device & 1) {
@@ -362,10 +363,8 @@ static int snd_card_dummy_playback_open(struct snd_pcm_substream *substream)
 	}
 	if (substream->pcm->device & 2)
 		runtime->hw.info &= ~(SNDRV_PCM_INFO_MMAP|SNDRV_PCM_INFO_MMAP_VALID);
-	if ((err = add_playback_constraints(runtime)) < 0) {
-		kfree(dpcm);
+	if ((err = add_playback_constraints(runtime)) < 0)
 		return err;
-	}
 
 	return 0;
 }
@@ -379,6 +378,7 @@ static int snd_card_dummy_capture_open(struct snd_pcm_substream *substream)
 	if ((dpcm = new_pcm_stream(substream)) == NULL)
 		return -ENOMEM;
 	runtime->private_data = dpcm;
+	/* makes the infrastructure responsible for freeing dpcm */
 	runtime->private_free = snd_card_dummy_runtime_free;
 	runtime->hw = snd_card_dummy_capture;
 	if (substream->pcm->device == 1) {
@@ -387,10 +387,8 @@ static int snd_card_dummy_capture_open(struct snd_pcm_substream *substream)
 	}
 	if (substream->pcm->device & 2)
 		runtime->hw.info &= ~(SNDRV_PCM_INFO_MMAP|SNDRV_PCM_INFO_MMAP_VALID);
-	if ((err = add_capture_constraints(runtime)) < 0) {
-		kfree(dpcm);
+	if ((err = add_capture_constraints(runtime)) < 0)
 		return err;
-	}
 
 	return 0;
 }