| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.14 052/164] ALSA: pcm: prevent UAF in snd_pcm_info | Date | Tue, 12 Dec 2017 13:43:52 +0100 |
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4.14-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 @@ -153,7 +153,9 @@ 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;
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