[PATCH 6.1 0583/1887] rxrpc: Fix delayed ACKs to not set the reference serial number

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Howells <dhowells@redhat.com>

[ Upstream commit e7870cf13d20f56bfc19f9c3e89707c69cf104ef ]

Fix the construction of delayed ACKs to not set the reference serial number
as they can't be used as an RTT reference.

Fixes: 17926a79320a ("[AF_RXRPC]: Provide secure RxRPC sockets for use by userspace and kernel both")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: linux-afs@lists.infradead.org
cc: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/rxrpc/output.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
index 08c117bc083ec..3d9032fae9d91 100644
--- a/net/rxrpc/output.c
+++ b/net/rxrpc/output.c
@@ -87,7 +87,7 @@ static size_t rxrpc_fill_out_ack(struct rxrpc_connection *conn,
 		return 0;
 
 	/* Barrier against rxrpc_input_data(). */
-	serial = call->ackr_serial;
+	serial = reason == RXRPC_ACK_DELAY ? 0 : call->ackr_serial;
 	hard_ack = READ_ONCE(call->rx_hard_ack);
 	top = smp_load_acquire(&call->rx_top);
 	*_hard_ack = hard_ack;
-- 
2.53.0