selinux: rate-limit netlink message warnings in selinux_nlmsg_perm()

Any process is able to send netlink messages with invalid types.
Make the warning rate-limited to prevent too much log spam.

The warning is supposed to help to find misbehaving programs, so
print the triggering command name and pid.
Reported-by: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
[PM: subject line tweak to make checkpatch.pl happy]
Signed-off-by: Paul Moore <pmoore@redhat.com>

security/selinux/hooks.c

@@ -4858,11 +4858,12 @@ static int selinux_nlmsg_perm(struct sock *sk, struct sk_buff *skb)
 	err = selinux_nlmsg_lookup(sksec->sclass, nlh->nlmsg_type, &perm);
 	if (err) {
 		if (err == -EINVAL) {
-			printk(KERN_WARNING
-			       "SELinux: unrecognized netlink message:"
-			       " protocol=%hu nlmsg_type=%hu sclass=%s\n",
+			pr_warn_ratelimited("SELinux: unrecognized netlink"
+			       " message: protocol=%hu nlmsg_type=%hu sclass=%s"
+			       " pig=%d comm=%s\n",
 			       sk->sk_protocol, nlh->nlmsg_type,
-			       secclass_map[sksec->sclass - 1].name);
+			       secclass_map[sksec->sclass - 1].name,
+			       task_pid_nr(current), current->comm);
 			if (!selinux_enforcing || security_get_allow_unknown())
 				err = 0;
 		}