This is a note to let you know that I've just added the patch titled ALSA: pcm: prevent UAF in snd_pcm_info to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: alsa-pcm-prevent-uaf-in-snd_pcm_info.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 362bca57f5d78220f8b5907b875961af9436e229 Mon Sep 17 00:00:00 2001 From: Robb Glasser <rglasser@xxxxxxxxxx> Date: Tue, 5 Dec 2017 09:16:55 -0800 Subject: ALSA: pcm: prevent UAF in snd_pcm_info From: Robb Glasser <rglasser@xxxxxxxxxx> 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 <rglasser@xxxxxxxxxx> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- sound/core/pcm.c | 2 ++ 1 file changed, 2 insertions(+) --- a/sound/core/pcm.c +++ b/sound/core/pcm.c @@ -149,7 +149,9 @@ static int snd_pcm_control_ioctl(struct 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; Patches currently in stable-queue which might be from rglasser@xxxxxxxxxx are queue-4.9/alsa-pcm-prevent-uaf-in-snd_pcm_info.patch