Re: [alsa-devel] [PATCH] ALSA: pcm: prevent UAF in snd_pcm_info

+ stable

On Tue, Dec 5, 2017 at 9:16 AM, Nick Desaulniers ndesaulniers@google.com wrote:

From: Robb Glasser rglasser@google.com

When the device descriptor is closed, the `substream->runtime` pointer is freed. But another thread may be in the ioctl handler, case SNDRV_CTL_IOCTL_PCM_INFO. This case calls snd_pcm_info_user() which calls snd_pcm_info() which accesses the now freed `substream->runtime`.

Signed-off-by: Robb Glasser rglasser@google.com Signed-off-by: Nick Desaulniers ndesaulniers@google.com

---

sound/core/pcm.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/sound/core/pcm.c b/sound/core/pcm.c index 9070f277f8db..09ee8c6b9f75 100644 --- a/sound/core/pcm.c +++ b/sound/core/pcm.c @@ -153,7 +153,9 @@ static int snd_pcm_control_ioctl(struct snd_card *card, err = -ENXIO; goto _error; }

•                   mutex_lock(&pcm->open_mutex);
                    err = snd_pcm_info_user(substream, info);
  

•                   mutex_unlock(&pcm->open_mutex);
            _error:
                    mutex_unlock(&register_mutex);
                    return err;
  

-- 2.15.0.531.g2ccb3012c9-goog