integrity: add validity checks for 'path' parameter

This patch adds validity checks for 'path' parameter and
makes it const.

Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

security/integrity/iint.c

@@ -213,6 +213,9 @@ int __init integrity_read_file(const char *path, char **data)
 	char *buf;
 	int rc = -EINVAL;
 
+	if (!path || !*path)
+		return -EINVAL;
+
 	file = filp_open(path, O_RDONLY, 0);
 	if (IS_ERR(file)) {
 		rc = PTR_ERR(file);