Smack: Lock mode for the floor and hat labels

The lock access mode allows setting a read lock on a file
for with the process has only read access. The floor label is
defined to make it easy to have the basic system installed such
that everyone can read it. Once there's a desire to read lock
(rationally or otherwise) a floor file a rule needs to get set.
This happens all the time, so make the floor label a little bit
more special and allow everyone lock access, too. By implication,
give processes with the hat label (hat can read everything)
lock access as well. This reduces clutter in the Smack rule set.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

security/smack/smack_access.c

@@ -142,8 +142,7 @@ int smk_access(struct smack_known *subject, struct smack_known *object,
 	 * Tasks cannot be assigned the internet label.
 	 * An internet subject can access any object.
 	 */
-	if (object == &smack_known_web ||
-	    subject == &smack_known_web)
+	if (object == &smack_known_web || subject == &smack_known_web)
 		goto out_audit;
 	/*
 	 * A star object can be accessed by any subject.
@@ -157,10 +156,11 @@ int smk_access(struct smack_known *subject, struct smack_known *object,
 	if (subject->smk_known == object->smk_known)
 		goto out_audit;
 	/*
-	 * A hat subject can read any object.
-	 * A floor object can be read by any subject.
+	 * A hat subject can read or lock any object.
+	 * A floor object can be read or locked by any subject.
 	 */
-	if ((request & MAY_ANYREAD) == request) {
+	if ((request & MAY_ANYREAD) == request ||
+	    (request & MAY_LOCK) == request) {
 		if (object == &smack_known_floor)
 			goto out_audit;
 		if (subject == &smack_known_hat)