Messages in this thread Patch in this message | | | From | Nick Desaulniers <> | Subject | [PATCH] ALSA: pcm: prevent UAF in snd_pcm_info | Date | Tue, 5 Dec 2017 09:16:55 -0800 |
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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(®ister_mutex); return err; -- 2.15.0.531.g2ccb3012c9-goog
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