netdev - [PATCH net-next 12/14] rxrpc: Don't transmit an ACK if there's no reason set

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Date:   Sun, 18 Sep 2016 00:19:07 +0100
From:   David Howells <dhowells@...hat.com>
To:     netdev@...r.kernel.org
Cc:     dhowells@...hat.com, linux-afs@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH net-next 12/14] rxrpc: Don't transmit an ACK if there's no
 reason set

Don't transmit an ACK if call->ackr_reason in unset.  There's the
possibility of a race between recvmsg() sending an ACK and the background
processing thread trying to send the same one.

Signed-off-by: David Howells <dhowells@...hat.com>
---

 net/rxrpc/output.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
index 06a9aca739d1..aa0507214b31 100644
--- a/net/rxrpc/output.c
+++ b/net/rxrpc/output.c
@@ -137,6 +137,11 @@ int rxrpc_send_call_packet(struct rxrpc_call *call, u8 type)
 	switch (type) {
 	case RXRPC_PACKET_TYPE_ACK:
 		spin_lock_bh(&call->lock);
+		if (!call->ackr_reason) {
+			spin_unlock_bh(&call->lock);
+			ret = 0;
+			goto out;
+		}
 		n = rxrpc_fill_out_ack(call, pkt);
 		call->ackr_reason = 0;