tls: splice_read: fix record type check

We don't support splicing control records. TLS 1.3 changes moved
the record type check into the decrypt if(). The skb may already
be decrypted and still be an alert.

Note that decrypt_skb_update() is idempotent and updates ctx->decrypted
so the if() is pointless.

Reorder the check for decryption errors with the content type check
while touching them. This part is not really a bug, because if
decryption failed in TLS 1.3 content type will be DATA, and for
TLS 1.2 it will be correct. Nevertheless its strange to touch output
before checking if the function has failed.

Fixes: fedf201 ("net: tls: Refactor control message handling on recv")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/tls/tls_sw.c

@@ -2018,21 +2018,18 @@ ssize_t tls_sw_splice_read(struct socket *sock,  loff_t *ppos,
 	if (!skb)
 		goto splice_read_end;
 
-	if (!ctx->decrypted) {
-		err = decrypt_skb_update(sk, skb, NULL, &chunk, &zc, false);
-
-		/* splice does not support reading control messages */
-		if (ctx->control != TLS_RECORD_TYPE_DATA) {
-			err = -EINVAL;
-			goto splice_read_end;
-		}
+	err = decrypt_skb_update(sk, skb, NULL, &chunk, &zc, false);
+	if (err < 0) {
+		tls_err_abort(sk, -EBADMSG);
+		goto splice_read_end;
+	}
 
-		if (err < 0) {
-			tls_err_abort(sk, -EBADMSG);
-			goto splice_read_end;
-		}
-		ctx->decrypted = 1;
+	/* splice does not support reading control messages */
+	if (ctx->control != TLS_RECORD_TYPE_DATA) {
+		err = -EINVAL;
+		goto splice_read_end;
 	}
+
 	rxm = strp_msg(skb);
 
 	chunk = min_t(unsigned int, rxm->full_len, len);