Merge branch 'kcm-data-races'

Eric Dumazet says:

====================
kcm: annotate data-races

This series address two different syzbot reports for KCM.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

Author: davem330

net/kcm/kcmsock.c

@@ -162,7 +162,8 @@ static void kcm_rcv_ready(struct kcm_sock *kcm)
 	/* Buffer limit is okay now, add to ready list */
 	list_add_tail(&kcm->wait_rx_list,
 		      &kcm->mux->kcm_rx_waiters);
-	kcm->rx_wait = true;
+	/* paired with lockless reads in kcm_rfree() */
+	WRITE_ONCE(kcm->rx_wait, true);
 }
 
 static void kcm_rfree(struct sk_buff *skb)
@@ -178,7 +179,7 @@ static void kcm_rfree(struct sk_buff *skb)
 	/* For reading rx_wait and rx_psock without holding lock */
 	smp_mb__after_atomic();
 
-	if (!kcm->rx_wait && !kcm->rx_psock &&
+	if (!READ_ONCE(kcm->rx_wait) && !READ_ONCE(kcm->rx_psock) &&
 	    sk_rmem_alloc_get(sk) < sk->sk_rcvlowat) {
 		spin_lock_bh(&mux->rx_lock);
 		kcm_rcv_ready(kcm);
@@ -237,7 +238,8 @@ static void requeue_rx_msgs(struct kcm_mux *mux, struct sk_buff_head *head)
 		if (kcm_queue_rcv_skb(&kcm->sk, skb)) {
 			/* Should mean socket buffer full */
 			list_del(&kcm->wait_rx_list);
-			kcm->rx_wait = false;
+			/* paired with lockless reads in kcm_rfree() */
+			WRITE_ONCE(kcm->rx_wait, false);
 
 			/* Commit rx_wait to read in kcm_free */
 			smp_wmb();
@@ -280,10 +282,12 @@ static struct kcm_sock *reserve_rx_kcm(struct kcm_psock *psock,
 	kcm = list_first_entry(&mux->kcm_rx_waiters,
 			       struct kcm_sock, wait_rx_list);
 	list_del(&kcm->wait_rx_list);
-	kcm->rx_wait = false;
+	/* paired with lockless reads in kcm_rfree() */
+	WRITE_ONCE(kcm->rx_wait, false);
 
 	psock->rx_kcm = kcm;
-	kcm->rx_psock = psock;
+	/* paired with lockless reads in kcm_rfree() */
+	WRITE_ONCE(kcm->rx_psock, psock);
 
 	spin_unlock_bh(&mux->rx_lock);
 
@@ -310,7 +314,8 @@ static void unreserve_rx_kcm(struct kcm_psock *psock,
 	spin_lock_bh(&mux->rx_lock);
 
 	psock->rx_kcm = NULL;
-	kcm->rx_psock = NULL;
+	/* paired with lockless reads in kcm_rfree() */
+	WRITE_ONCE(kcm->rx_psock, NULL);
 
 	/* Commit kcm->rx_psock before sk_rmem_alloc_get to sync with
 	 * kcm_rfree
@@ -1240,7 +1245,8 @@ static void kcm_recv_disable(struct kcm_sock *kcm)
 	if (!kcm->rx_psock) {
 		if (kcm->rx_wait) {
 			list_del(&kcm->wait_rx_list);
-			kcm->rx_wait = false;
+			/* paired with lockless reads in kcm_rfree() */
+			WRITE_ONCE(kcm->rx_wait, false);
 		}
 
 		requeue_rx_msgs(mux, &kcm->sk.sk_receive_queue);
@@ -1793,7 +1799,8 @@ static void kcm_done(struct kcm_sock *kcm)
 
 	if (kcm->rx_wait) {
 		list_del(&kcm->wait_rx_list);
-		kcm->rx_wait = false;
+		/* paired with lockless reads in kcm_rfree() */
+		WRITE_ONCE(kcm->rx_wait, false);
 	}
 	/* Move any pending receive messages to other kcm sockets */
 	requeue_rx_msgs(mux, &sk->sk_receive_queue);