tls: return -EBUSY if crypto_info is already set

do_tls_setsockopt_tx returns 0 without doing anything when crypto_info
is already set. Silent failure is confusing for users.

Fixes: 3c4d7559 ("tls: kernel TLS support")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tls/tls_main.c

@@ -367,8 +367,10 @@ static int do_tls_setsockopt_tx(struct sock *sk, char __user *optval,
 
 	crypto_info = &ctx->crypto_send;
 	/* Currently we don't support set crypto info more than one time */
-	if (TLS_CRYPTO_INFO_READY(crypto_info))
+	if (TLS_CRYPTO_INFO_READY(crypto_info)) {
+		rc = -EBUSY;
 		goto out;
+	}
 
 	rc = copy_from_user(crypto_info, optval, sizeof(*crypto_info));
 	if (rc) {