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ALSA: pcm: prevent UAF in snd_pcm_info

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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`.

Bug: 36006981
Signed-off-by: Robb Glasser <rglasser@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Change-Id: I445d24bc21dc0af6d9522a8daabe64969042236a
This commit is contained in:
Robb Glasser 2017-08-11 11:33:31 -07:00 committed by Artem Borisov
parent 277389dc14
commit 745b477c70
1 changed files with 2 additions and 0 deletions
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2
sound/core/pcm.c
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@ -146,7 +146,9 @@ static int snd_pcm_control_ioctl(struct snd_card *card,
err = -ENXIO; err = -ENXIO;
goto _error; goto _error;
} }
mutex_lock(&pcm->open_mutex);
err = snd_pcm_info_user(substream, info); err = snd_pcm_info_user(substream, info);
mutex_unlock(&pcm->open_mutex);
_error: _error:
mutex_unlock(&register_mutex); mutex_unlock(&register_mutex);
return err; return err;