tls: Fix mixing between async capable and async

Today, tls_sw_recvmsg is capable of using asynchronous mode to handle
application data TLS records. Moreover, it assumes that if the cipher
can be handled asynchronously, then all packets will be processed
asynchronously.

However, this assumption is not always true. Specifically, for AES-GCM
in TLS1.2, it causes data corruption, and breaks user applications.

This patch fixes this problem by separating the async capability from
the decryption operation result.

Fixes: c0ab4732 ("net/tls: Do not use async crypto for non-data records")
Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Reviewed-by: Boris Pismenny <borisp@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tls/tls_sw.c

@@ -1693,7 +1693,8 @@ int tls_sw_recvmsg(struct sock *sk,
 		bool zc = false;
 		int to_decrypt;
 		int chunk = 0;
-		bool async;
+		bool async_capable;
+		bool async = false;
 
 		skb = tls_wait_data(sk, psock, flags, timeo, &err);
 		if (!skb) {
@@ -1727,21 +1728,23 @@ int tls_sw_recvmsg(struct sock *sk,
 
 		/* Do not use async mode if record is non-data */
 		if (ctx->control == TLS_RECORD_TYPE_DATA)
-			async = ctx->async_capable;
+			async_capable = ctx->async_capable;
 		else
-			async = false;
+			async_capable = false;
 
 		err = decrypt_skb_update(sk, skb, &msg->msg_iter,
-					 &chunk, &zc, async);
+					 &chunk, &zc, async_capable);
 		if (err < 0 && err != -EINPROGRESS) {
 			tls_err_abort(sk, EBADMSG);
 			goto recv_end;
 		}
 
-		if (err == -EINPROGRESS)
+		if (err == -EINPROGRESS) {
+			async = true;
 			num_async++;
-		else if (prot->version == TLS_1_3_VERSION)
+		} else if (prot->version == TLS_1_3_VERSION) {
 			tlm->control = ctx->control;
+		}
 
 		/* If the type of records being processed is not known yet,
 		 * set it to record type just dequeued. If it is already known,