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 <daniel.thompson@st.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c
index c873243..4f900d8 100644 (file)
--- 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;
 }