tls: get psock ref after taking rxlock to avoid leak

At the start of tls_sw_recvmsg, we take a reference on the psock, and
then call tls_rx_reader_lock. If that fails, we return directly
without releasing the reference.

Instead of adding a new label, just take the reference after locking
has succeeded, since we don't need it before.

Fixes: 4cbc325 ("tls: rx: allow only one reader at a time")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/fe2ade22d030051ce4c3638704ed58b67d0df643.1711120964.git.sd@queasysnail.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/tls/tls_sw.c

@@ -1976,10 +1976,10 @@ int tls_sw_recvmsg(struct sock *sk,
 	if (unlikely(flags & MSG_ERRQUEUE))
 		return sock_recv_errqueue(sk, msg, len, SOL_IP, IP_RECVERR);
 
-	psock = sk_psock_get(sk);
 	err = tls_rx_reader_lock(sk, ctx, flags & MSG_DONTWAIT);
 	if (err < 0)
 		return err;
+	psock = sk_psock_get(sk);
 	bpf_strp_enabled = sk_psock_strp_enabled(psock);
 
 	/* If crypto failed the connection is broken */