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>

1 files changed, 4 insertions, 6 deletions

diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c
index c873243e6713..4f900d8b92ce 100644
--- 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;
 }