nvmet-tcp: fix callback lock for TLS handshake

JIRA: https://issues.redhat.com/browse/RHEL-110941

When restoring the default socket callbacks during a TLS handshake, we
need to acquire a write lock on sk_callback_lock.  Previously, a read
lock was used, which is insufficient for modifying sk_user_data and
sk_data_ready.

Fixes: 675b453 ("nvmet-tcp: enable TLS handshake upcall")
Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
(cherry picked from commit 0523c6c)
Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>

Author: maurizio-lombardi

drivers/nvme/target/tcp.c

@@ -1928,10 +1928,10 @@ static void nvmet_tcp_alloc_queue(struct nvmet_tcp_port *port,
 		struct sock *sk = queue->sock->sk;
 
 		/* Restore the default callbacks before starting upcall */
-		read_lock_bh(&sk->sk_callback_lock);
+		write_lock_bh(&sk->sk_callback_lock);
 		sk->sk_user_data = NULL;
 		sk->sk_data_ready = port->data_ready;
-		read_unlock_bh(&sk->sk_callback_lock);
+		write_unlock_bh(&sk->sk_callback_lock);
 		if (!nvmet_tcp_try_peek_pdu(queue)) {
 			if (!nvmet_tcp_tls_handshake(queue))
 				return;