From c51f80d4d3a47dbc97b9b1b67d81e763afe9c398 Mon Sep 17 00:00:00 2001 From: Robb Glasser Date: Tue, 5 Dec 2017 09:16:55 -0800 Subject: [PATCH] ALSA: pcm: prevent UAF in snd_pcm_info commit 362bca57f5d78220f8b5907b875961af9436e229 upstream. 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`. Note: this fixes CVE-2017-0861 Signed-off-by: Robb Glasser Signed-off-by: Nick Desaulniers Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings --- sound/core/pcm.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/sound/core/pcm.c b/sound/core/pcm.c index 13eaeb353d28..00905d128b94 100644 --- a/sound/core/pcm.c +++ b/sound/core/pcm.c @@ -145,7 +145,9 @@ 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; -- 2.39.2