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ALSA: pcm: prevent UAF in snd_pcm_info 

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Robb Glasser 2017-12-05 09:16:55 -08:00 committed by Takashi Iwai
parent f429e7e494
commit 362bca57f5
1 changed files with 2 additions and 0 deletions
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2
sound/core/pcm.c
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@ -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(&register_mutex);
return err;