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Subject[PATCH] 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>
---
sound/drivers/dummy.c | 10 ++++------
1 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c
index 4e4c69e..90fc1ce 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;
}
--
1.5.5.1


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