Merge branch 'mptcp-fixes'

Jeremy Kerr says:

====================
net: mctp: struct sock lifetime fixes

This series is a set of fixes for the sock lifetime handling in the
AF_MCTP code, fixing a uaf reported by Noam Rathaus
<[e-mail]>.

The Fixes: tags indicate the original patches affected, but some
tweaking to backport to those commits may be needed; I have a separate
branch with backports to 5.15 if that helps with stable trees.

Of course, any comments/queries most welcome.
====================

Signed-off-by: David S. Miller <[e-mail]>

net/mctp/af_mctp.c

···
 
 static void mctp_sk_close(struct sock *sk, long timeout)
 {
-	struct mctp_sock *msk = container_of(sk, struct mctp_sock, sk);
-
-	del_timer_sync(&msk->key_expiry);
 	sk_common_release(sk);
 }
 
···
 		spin_lock_irqsave(&key->lock, fl2);
 		__mctp_key_remove(key, net, fl2, MCTP_TRACE_KEY_CLOSED);
 	}
+	sock_set_flag(sk, SOCK_DEAD);
 	spin_unlock_irqrestore(&net->mctp.keys_lock, flags);
+
+	/* Since there are no more tag allocations (we have removed all of the
+	 * keys), stop any pending expiry events. the timer cannot be re-queued
+	 * as the sk is no longer observable
+	 */
+	del_timer_sync(&msk->key_expiry);
 }
 
 static struct proto mctp_proto = {

net/mctp/route.c

···
 	key->valid = true;
 	spin_lock_init(&key->lock);
 	refcount_set(&key->refs, 1);
+	sock_hold(key->sk);
 
 	return key;
 }
···
 	mctp_dev_release_key(key->dev, key);
 	spin_unlock_irqrestore(&key->lock, flags);
 
+	sock_put(key->sk);
 	kfree(key);
 }
 
···
 	int rc = 0;
 
 	spin_lock_irqsave(&net->mctp.keys_lock, flags);
+
+	if (sock_flag(&msk->sk, SOCK_DEAD)) {
+		rc = -EINVAL;
+		goto out_unlock;
+	}
 
 	hlist_for_each_entry(tmp, &net->mctp.keys, hlist) {
 		if (mctp_key_match(tmp, key->local_addr, key->peer_addr,
···
 		hlist_add_head(&key->sklist, &msk->keys);
 	}
 
+out_unlock:
 	spin_unlock_irqrestore(&net->mctp.keys_lock, flags);
 
 	return rc;
···
 
 static int mctp_route_input(struct mctp_route *route, struct sk_buff *skb)
 {
+	struct mctp_sk_key *key, *any_key = NULL;
 	struct net *net = dev_net(skb->dev);
-	struct mctp_sk_key *key;
 	struct mctp_sock *msk;
 	struct mctp_hdr *mh;
 	unsigned long f;
···
 			 * key for reassembly - we'll create a more specific
 			 * one for future packets if required (ie, !EOM).
 			 */
-			key = mctp_lookup_key(net, skb, MCTP_ADDR_ANY, &f);
-			if (key) {
-				msk = container_of(key->sk,
+			any_key = mctp_lookup_key(net, skb, MCTP_ADDR_ANY, &f);
+			if (any_key) {
+				msk = container_of(any_key->sk,
 						   struct mctp_sock, sk);
-				spin_unlock_irqrestore(&key->lock, f);
-				mctp_key_unref(key);
-				key = NULL;
+				spin_unlock_irqrestore(&any_key->lock, f);
 			}
 		}
 
···
 			 * this function.
 			 */
 			rc = mctp_key_add(key, msk);
-			if (rc) {
-				kfree(key);
-			} else {
+			if (!rc)
 				trace_mctp_key_acquire(key);
 
-				/* we don't need to release key->lock on exit */
-				mctp_key_unref(key);
-			}
+			/* we don't need to release key->lock on exit, so
+			 * clean up here and suppress the unlock via
+			 * setting to NULL
+			 */
+			mctp_key_unref(key);
 			key = NULL;
 
 		} else {
···
 		spin_unlock_irqrestore(&key->lock, f);
 		mctp_key_unref(key);
 	}
+	if (any_key)
+		mctp_key_unref(any_key);
 out:
 	if (rc)
 		kfree_skb(skb);