Merge branch 'net-tls-redo-the-RX-resync-locking'

Jakub Kicinski says:

====================
net/tls: redo the RX resync locking

Take two of making sure we don't use a NULL netdev pointer
for RX resync.  This time using a bit and an open coded
wait loop.

v2:
 - fix build warning (DaveM).
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tls.h

@@ -209,6 +209,10 @@ struct tls_offload_context_tx {
 	(ALIGN(sizeof(struct tls_offload_context_tx), sizeof(void *)) +        \
 	 TLS_DRIVER_STATE_SIZE)
 
+enum tls_context_flags {
+	TLS_RX_SYNC_RUNNING = 0,
+};
+
 struct cipher_context {
 	char *iv;
 	char *rec_seq;

net/tls/tls_device.c

@@ -550,11 +550,23 @@ void tls_device_write_space(struct sock *sk, struct tls_context *ctx)
 	}
 }
 
+static void tls_device_resync_rx(struct tls_context *tls_ctx,
+				 struct sock *sk, u32 seq, u64 rcd_sn)
+{
+	struct net_device *netdev;
+
+	if (WARN_ON(test_and_set_bit(TLS_RX_SYNC_RUNNING, &tls_ctx->flags)))
+		return;
+	netdev = READ_ONCE(tls_ctx->netdev);
+	if (netdev)
+		netdev->tlsdev_ops->tls_dev_resync_rx(netdev, sk, seq, rcd_sn);
+	clear_bit_unlock(TLS_RX_SYNC_RUNNING, &tls_ctx->flags);
+}
+
 void handle_device_resync(struct sock *sk, u32 seq, u64 rcd_sn)
 {
 	struct tls_context *tls_ctx = tls_get_ctx(sk);
 	struct tls_offload_context_rx *rx_ctx;
-	struct net_device *netdev;
 	u32 is_req_pending;
 	s64 resync_req;
 	u32 req_seq;
@@ -570,12 +582,7 @@ void handle_device_resync(struct sock *sk, u32 seq, u64 rcd_sn)
 	if (unlikely(is_req_pending) && req_seq == seq &&
 	    atomic64_try_cmpxchg(&rx_ctx->resync_req, &resync_req, 0)) {
 		seq += TLS_HEADER_SIZE - 1;
-		down_read(&device_offload_lock);
-		netdev = tls_ctx->netdev;
-		if (netdev)
-			netdev->tlsdev_ops->tls_dev_resync_rx(netdev, sk, seq,
-							      rcd_sn);
-		up_read(&device_offload_lock);
+		tls_device_resync_rx(tls_ctx, sk, seq, rcd_sn);
 	}
 }
 
@@ -977,7 +984,10 @@ static int tls_device_down(struct net_device *netdev)
 		if (ctx->rx_conf == TLS_HW)
 			netdev->tlsdev_ops->tls_dev_del(netdev, ctx,
 							TLS_OFFLOAD_CTX_DIR_RX);
-		ctx->netdev = NULL;
+		WRITE_ONCE(ctx->netdev, NULL);
+		smp_mb__before_atomic(); /* pairs with test_and_set_bit() */
+		while (test_bit(TLS_RX_SYNC_RUNNING, &ctx->flags))
+			usleep_range(10, 200);
 		dev_put(netdev);
 		list_del_init(&ctx->list);