fs/squashfs: sqfs_concat_tokens: check if malloc succeeds

memory allocation should always be checked
Reviewed-by: Joao Marcos Costa <jmcosta944@gmail.com>
Signed-off-by: Richard Genoud <richard.genoud@posteo.net>

fs/squashfs/sqfs.c

@@ -242,6 +242,9 @@ static char *sqfs_concat_tokens(char **token_list, int token_count)
 	length = sqfs_get_tokens_length(token_list, token_count);
 
 	result = malloc(length + 1);
+	if (!result)
+		return NULL;
+
 	result[length] = '\0';
 
 	for (i = 0; i < token_count; i++) {