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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 1fa4445f9a ("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: Clement Lecigne <clecigne@google.com>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20230113120745.25464-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Clement Lecigne 2023-01-13 13:07:45 +01:00 committed by Takashi Iwai
parent 92a9c0ad86
commit 56b88b5056
1 changed files with 15 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
sound/core/control.c
View File

@ -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;