lzo: add a function to check the validity of the header

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

include/linux/lzo.h

@@ -31,6 +31,9 @@ int lzo1x_decompress_safe(const unsigned char *src, size_t src_len,
 int lzop_decompress(const unsigned char *src, size_t src_len,
 		    unsigned char *dst, size_t *dst_len);
 
+/* check if the header is valid (based on magic numbers) */
+bool lzop_is_valid_header(const unsigned char *src);
+
 /*
  * Return values (< 0 = Error)
  */

lib/lzo/lzo1x_decompress.c

@@ -30,16 +30,29 @@ static const unsigned char lzop_magic[] = {
 
 #define HEADER_HAS_FILTER	0x00000800L
 
-static inline const unsigned char *parse_header(const unsigned char *src)
+
+bool lzop_is_valid_header(const unsigned char *src)
 {
-	u16 version;
 	int i;
-
 	/* read magic: 9 first bytes */
 	for (i = 0; i < ARRAY_SIZE(lzop_magic); i++) {
 		if (*src++ != lzop_magic[i])
-			return NULL;
+			return false;
 	}
+	return true;
+}
+
+static inline const unsigned char *parse_header(const unsigned char *src)
+{
+	u16 version;
+	int i;
+
+	if (!lzop_is_valid_header(src))
+		return NULL;
+
+	/* skip header */
+	src += 9;
+
 	/* get version (2bytes), skip library version (2),
 	 * 'need to be extracted' version (2) and
 	 * method (1) */