ASoC: SOF: control: fix size checks for volatile ext_bytes control .get()

Mirror addition of checks for regular ext_bytes controls.

Fixes: 783560d0 ('ASoC: SOF: Implement snd_sof_bytes_ext_volatile_get kcontrol IO')
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20200921110814.2910477-3-kai.vehmanen@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/control.c

@@ -369,6 +369,14 @@ int snd_sof_bytes_ext_volatile_get(struct snd_kcontrol *kcontrol, unsigned int _
 	int ret;
 	int err;
 
+	/*
+	 * Decrement the limit by ext bytes header size to
+	 * ensure the user space buffer is not exceeded.
+	 */
+	if (size < sizeof(struct snd_ctl_tlv))
+		return -ENOSPC;
+	size -= sizeof(struct snd_ctl_tlv);
+
 	ret = pm_runtime_get_sync(scomp->dev);
 	if (ret < 0 && ret != -EACCES) {
 		dev_err_ratelimited(scomp->dev, "error: bytes_ext get failed to resume %d\n", ret);
@@ -396,6 +404,12 @@ int snd_sof_bytes_ext_volatile_get(struct snd_kcontrol *kcontrol, unsigned int _
 
 	data_size = cdata->data->size + sizeof(const struct sof_abi_hdr);
 
+	/* make sure we don't exceed size provided by user space for data */
+	if (data_size > size) {
+		ret = -ENOSPC;
+		goto out;
+	}
+
 	header.numid = scontrol->cmd;
 	header.length = data_size;
 	if (copy_to_user(tlvd, &header, sizeof(const struct snd_ctl_tlv))) {