4.4-stable review patch. If anyone has any objections, please let me know.
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From: Robb Glasser rglasser@google.com
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@google.com Signed-off-by: Nick Desaulniers ndesaulniers@google.com Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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;