ALSA: control: Don't access controls outside of protected regions
A control that is visible on the card->controls list can be freed at any time.
This means we must not access any of its memory while not holding the
controls_rw_lock. Otherwise we risk a use after free access.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Jaroslav Kysela <perex@perex.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/control.c b/sound/core/control.c
index 1f413c2..5c49f97 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -330,6 +330,7 @@
{
struct snd_ctl_elem_id id;
unsigned int idx;
+ unsigned int count;
int err = -EINVAL;
if (! kcontrol)
@@ -358,8 +359,9 @@
card->controls_count += kcontrol->count;
kcontrol->id.numid = card->last_numid + 1;
card->last_numid += kcontrol->count;
+ count = kcontrol->count;
up_write(&card->controls_rwsem);
- for (idx = 0; idx < kcontrol->count; idx++, id.index++, id.numid++)
+ for (idx = 0; idx < count; idx++, id.index++, id.numid++)
snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_ADD, &id);
return 0;
@@ -388,6 +390,7 @@
bool add_on_replace)
{
struct snd_ctl_elem_id id;
+ unsigned int count;
unsigned int idx;
struct snd_kcontrol *old;
int ret;
@@ -423,8 +426,9 @@
card->controls_count += kcontrol->count;
kcontrol->id.numid = card->last_numid + 1;
card->last_numid += kcontrol->count;
+ count = kcontrol->count;
up_write(&card->controls_rwsem);
- for (idx = 0; idx < kcontrol->count; idx++, id.index++, id.numid++)
+ for (idx = 0; idx < count; idx++, id.index++, id.numid++)
snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_ADD, &id);
return 0;
@@ -897,9 +901,9 @@
result = kctl->put(kctl, control);
}
if (result > 0) {
+ struct snd_ctl_elem_id id = control->id;
up_read(&card->controls_rwsem);
- snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE,
- &control->id);
+ snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_VALUE, &id);
return 0;
}
}
@@ -1333,8 +1337,9 @@
}
err = kctl->tlv.c(kctl, op_flag, tlv.length, _tlv->tlv);
if (err > 0) {
+ struct snd_ctl_elem_id id = kctl->id;
up_read(&card->controls_rwsem);
- snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_TLV, &kctl->id);
+ snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_TLV, &id);
return 0;
}
} else {