apparmor: fix memory leak when deduping profile load

AppArmor is leaking the newly loaded profile and its proxy when
the profile is an exact match to the currently loaded version.

In this case the dedup check results in the profile being skipped and
put without dealing with the proxy ref thus not breaking a circular
refcount and causing a leak.

BugLink: http://bugs.launchpad.net/bugs/1750594
Fixes: 5d5182cae401 ("apparmor: move to per loaddata files, instead of replicating in profiles")
Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/policy.c

@@ -1008,6 +1008,9 @@ ssize_t aa_replace_profiles(struct aa_ns *policy_ns, struct aa_label *label,
 			audit_policy(label, op, ns_name, ent->new->base.hname,
 				     "same as current profile, skipping",
 				     error);
+			/* break refcount cycle with proxy. */
+			aa_put_proxy(ent->new->label.proxy);
+			ent->new->label.proxy = NULL;
 			goto skip;
 		}