ASoC: SOF: Add some bounds checking to firmware data

Smatch complains about "head->full_size - head->header_size" can
underflow.  To some extent, we're always going to have to trust the
firmware a bit.  However, it's easy enough to add a check for negatives,
and let's add a upper bounds check as well.

Fixes: d2458baa ("ASoC: SOF: ipc3-loader: Implement firmware parsing and loading")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://msgid.link/r/5593d147-058c-4de3-a6f5-540ecb96f6f8@moroto.mountainSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/ipc3-loader.c

@@ -148,6 +148,8 @@ static size_t sof_ipc3_fw_parse_ext_man(struct snd_sof_dev *sdev)
 
 	head = (struct sof_ext_man_header *)fw->data;
 	remaining = head->full_size - head->header_size;
+	if (remaining < 0 || remaining > sdev->basefw.fw->size)
+		return -EINVAL;
 	ext_man_size = ipc3_fw_ext_man_size(sdev, fw);
 
 	/* Assert firmware starts with extended manifest */