Commit 56b88b50 authored by Clement Lecigne's avatar Clement Lecigne Committed by Takashi Iwai
Browse files

ALSA: pcm: Move rwsem lock inside snd_ctl_elem_read to prevent UAF 



Takes rwsem lock inside snd_ctl_elem_read instead of snd_ctl_elem_read_user
like it was done for write in commit 1fa4445f ("ALSA: control - introduce
snd_ctl_notify_one() helper"). Doing this way we are also fixing the following
locking issue happening in the compat path which can be easily triggered and
turned into an use-after-free.

64-bits:
snd_ctl_ioctl
  snd_ctl_elem_read_user
    [takes controls_rwsem]
    snd_ctl_elem_read [lock properly held, all good]
    [drops controls_rwsem]

32-bits:
snd_ctl_ioctl_compat
  snd_ctl_elem_write_read_compat
    ctl_elem_write_read
      snd_ctl_elem_read [missing lock, not good]

CVE-2023-0266 was assigned for this issue.

Cc: stable@kernel.org # 5.13+
Signed-off-by: default avatarClement Lecigne <clecigne@google.com>
Reviewed-by: default avatarJaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20230113120745.25464-1-tiwai@suse.de


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 92a9c0ad

sound/core/control.c

+15 −9
Original line number Diff line number Diff line
@@ -1203,14 +1203,19 @@ static int snd_ctl_elem_read(struct snd_card *card, 
	const u32 pattern = 0xdeadbeef;

	int ret;



	down_read(&card->controls_rwsem);

	kctl = snd_ctl_find_id(card, &control->id);

	if (kctl == NULL)

		return -ENOENT;

	if (kctl == NULL) {

		ret = -ENOENT;

		goto unlock;

	}



	index_offset = snd_ctl_get_ioff(kctl, &control->id);

	vd = &kctl->vd[index_offset];

	if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_READ) || kctl->get == NULL)

		return -EPERM;

	if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_READ) || kctl->get == NULL) {

		ret = -EPERM;

		goto unlock;

	}



	snd_ctl_build_ioff(&control->id, kctl, index_offset);
@@ -1220,7 +1225,7 @@ static int snd_ctl_elem_read(struct snd_card *card, 
	info.id = control->id;

	ret = __snd_ctl_elem_info(card, kctl, &info, NULL);

	if (ret < 0)

		return ret;

		goto unlock;

#endif



	if (!snd_ctl_skip_validation(&info))
@@ -1230,7 +1235,7 @@ static int snd_ctl_elem_read(struct snd_card *card, 
		ret = kctl->get(kctl, control);

	snd_power_unref(card);

	if (ret < 0)

		return ret;

		goto unlock;

	if (!snd_ctl_skip_validation(&info) &&

	    sanity_check_elem_value(card, control, &info, pattern) < 0) {

		dev_err(card->dev,
@@ -1238,8 +1243,11 @@ static int snd_ctl_elem_read(struct snd_card *card, 
			control->id.iface, control->id.device,

			control->id.subdevice, control->id.name,

			control->id.index);

		return -EINVAL;

		ret = -EINVAL;

		goto unlock;

	}

unlock:

	up_read(&card->controls_rwsem);

	return ret;

}
@@ -1253,9 +1261,7 @@ static int snd_ctl_elem_read_user(struct snd_card *card, 
	if (IS_ERR(control))

		return PTR_ERR(control);



	down_read(&card->controls_rwsem);

	result = snd_ctl_elem_read(card, control);

	up_read(&card->controls_rwsem);

	if (result < 0)

		goto error;