[PATCH net v2 06/10] rxrpc: Fix the reception of a reply packet before data transmission

[David Howells <dhowells@redhat.com>]

Fix rxrpc_receiving_reply() to handle the reception of an apparent reply
DATA packet before rxrpc has had a chance to send any request DATA packets
on a client call by checking to see if the call has been exposed yet by
sending the first packet.

Without this, rxrpc_rotate_tx_window() might oops.

Also fix rxrpc_rotate_tx_window() to handle the Tx queue being empty by
changing the do...while loop into a while loop, just in case a call is
abnormally terminated by an early reply before the last request packet is
transmitted.

Fixes: b341a0263b1b ("rxrpc: Implement progressive transmission queue struct")
Link: https://sashiko.dev/#/patchset/20260616155749.2125907-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jeffrey Altman <jaltman@auristor.com>
cc: Eric Dumazet <edumazet@google.com>
cc: "David S. Miller" <davem@davemloft.net>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: stable@kernel.org
---
 net/rxrpc/input.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index 37881dffa898..01ccd2d2fe92 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -247,7 +247,7 @@ static bool rxrpc_rotate_tx_window(struct rxrpc_call *call, rxrpc_seq_t to,
 		tq = call->tx_queue;
 	}
 
-	do {
+	while (before_eq(seq, to)) {
 		unsigned int ix = seq - call->tx_qbase;
 
 		_debug("tq=%x seq=%x i=%d f=%x", tq->qbase, seq, ix, tq->bufs[ix]->flags);
@@ -317,8 +317,7 @@ static bool rxrpc_rotate_tx_window(struct rxrpc_call *call, rxrpc_seq_t to,
 				break;
 			}
 		}
-
-	} while (before_eq(seq, to));
+	}
 
 	if (trace)
 		trace_rxrpc_rack_update(call, summary);
@@ -392,6 +391,14 @@ static bool rxrpc_receiving_reply(struct rxrpc_call *call)
 		trace_rxrpc_timer_can(call, rxrpc_timer_trace_delayed_ack);
 	}
 
+	/* Deal with an apparent reply coming in before we've got the request
+	 * queued or transmitted.
+	 */
+	if (!test_bit(RXRPC_CALL_EXPOSED, &call->flags)) {
+		rxrpc_proto_abort(call, top, rxrpc_eproto_early_reply);
+		return false;
+	}
+
 	if (!test_bit(RXRPC_CALL_TX_LAST, &call->flags)) {
 		if (!rxrpc_rotate_tx_window(call, top, &summary)) {
 			rxrpc_proto_abort(call, top, rxrpc_eproto_early_reply);