rxrpc: Fix re-decryption of RESPONSE packets

commit 0422e7a upstream.

If a RESPONSE packet gets a temporary failure during processing, it may end
up in a partially decrypted state - and then get requeued for a retry.

Fix this by just discarding the packet; we will send another CHALLENGE
packet and thereby elicit a further response.  Similarly, discard an
incoming CHALLENGE packet if we get an error whilst generating a RESPONSE;
the server will send another CHALLENGE.

Fixes: 17926a7 ("[AF_RXRPC]: Provide secure RxRPC sockets for use by userspace and kernel both")
Closes: https://sashiko.dev/#/patchset/20260422161438.2593376-4-dhowells@redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jeffrey Altman <jaltman@auristor.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: stable@kernel.org
Link: https://patch.msgid.link/20260423200909.3049438-3-dhowells@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: dhowells

include/trace/events/rxrpc.h

@@ -232,7 +232,6 @@
 	EM(rxrpc_conn_put_unidle,		"PUT unidle  ") \
 	EM(rxrpc_conn_put_work,			"PUT work    ") \
 	EM(rxrpc_conn_queue_challenge,		"QUE chall   ") \
-	EM(rxrpc_conn_queue_retry_work,		"QUE retry-wk") \
 	EM(rxrpc_conn_queue_rx_work,		"QUE rx-work ") \
 	EM(rxrpc_conn_see_new_service_conn,	"SEE new-svc ") \
 	EM(rxrpc_conn_see_reap_service,		"SEE reap-svc") \

net/rxrpc/conn_event.c

@@ -344,7 +344,6 @@ void rxrpc_process_delayed_final_acks(struct rxrpc_connection *conn, bool force)
 static void rxrpc_do_process_connection(struct rxrpc_connection *conn)
 {
 	struct sk_buff *skb;
-	int ret;
 
 	if (test_and_clear_bit(RXRPC_CONN_EV_CHALLENGE, &conn->events))
 		rxrpc_secure_connection(conn);
@@ -353,17 +352,8 @@ static void rxrpc_do_process_connection(struct rxrpc_connection *conn)
 	 * connection that each one has when we've finished with it */
 	while ((skb = skb_dequeue(&conn->rx_queue))) {
 		rxrpc_see_skb(skb, rxrpc_skb_see_conn_work);
-		ret = rxrpc_process_event(conn, skb);
-		switch (ret) {
-		case -ENOMEM:
-		case -EAGAIN:
-			skb_queue_head(&conn->rx_queue, skb);
-			rxrpc_queue_conn(conn, rxrpc_conn_queue_retry_work);
-			break;
-		default:
-			rxrpc_free_skb(skb, rxrpc_skb_put_conn_work);
-			break;
-		}
+		rxrpc_process_event(conn, skb);
+		rxrpc_free_skb(skb, rxrpc_skb_put_conn_work);
 	}
 }