ima: ignore empty and with whitespaces policy lines

Empty policy lines cause parsing failures which is, especially
for new users, hard to spot. This patch prevents it.

Changes in v2:
* strip leading blanks and tabs in rules to prevent parsing failures
Signed-off-by: NDmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: NMimi Zohar <zohar@linux.vnet.ibm.com>

security/integrity/ima/ima_policy.c

@@ -696,8 +696,9 @@ ssize_t ima_parse_add_rule(char *rule)
 
 	p = strsep(&rule, "\n");
 	len = strlen(p) + 1;
+	p += strspn(p, " \t");
 
-	if (*p == '#')
+	if (*p == '#' || *p == '\0')
 		return len;
 
 	entry = kzalloc(sizeof(*entry), GFP_KERNEL);