smex: reject undersized fw-ready section

The fw-ready section was cast to a struct and field-read without
checking its size, reading past a short section. Reject a section
smaller than the struct.

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Author: lrgirdwo

smex/ldc.c

@@ -26,6 +26,13 @@ static int fw_version_copy(const struct elf_module *src,
 	if (section_size < 0)
 		return section_size;
 
+	if ((size_t)section_size < sizeof(struct sof_ipc_fw_ready)) {
+		fprintf(stderr, "error: .fw_ready section too small: %d\n",
+			section_size);
+		free(buffer);
+		return -EINVAL;
+	}
+
 	memcpy(&header->version,
 	       &((struct sof_ipc_fw_ready *)buffer)->version,
 	       sizeof(header->version));