rxrpc: Fix uninitialised variable in rxrpc_send_data()

Fix the uninitialised txb variable in rxrpc_send_data() by moving the code
that loads it above all the jumps to maybe_error, txb being stored back
into call->tx_pending right before the normal return.

Fixes: b0f571e ("rxrpc: Fix locking in rxrpc's sendmsg")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lists.infradead.org/pipermail/linux-afs/2024-October/008896.html
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://patch.msgid.link/20241001132702.3122709-3-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: dhowells

net/rxrpc/sendmsg.c

@@ -303,6 +303,11 @@ static int rxrpc_send_data(struct rxrpc_sock *rx,
 	sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
 
 reload:
+	txb = call->tx_pending;
+	call->tx_pending = NULL;
+	if (txb)
+		rxrpc_see_txbuf(txb, rxrpc_txbuf_see_send_more);
+
 	ret = -EPIPE;
 	if (sk->sk_shutdown & SEND_SHUTDOWN)
 		goto maybe_error;
@@ -329,11 +334,6 @@ static int rxrpc_send_data(struct rxrpc_sock *rx,
 			goto maybe_error;
 	}
 
-	txb = call->tx_pending;
-	call->tx_pending = NULL;
-	if (txb)
-		rxrpc_see_txbuf(txb, rxrpc_txbuf_see_send_more);
-
 	do {
 		if (!txb) {
 			size_t remain;