linux-kernel - [PATCH net 2/4] rxrpc: Fix insufficient receive notification generation

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Message-ID: <158047736987.133127.18071443288095328152.stgit@warthog.procyon.org.uk>
Date:   Fri, 31 Jan 2020 13:29:29 +0000
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 2/4] rxrpc: Fix insufficient receive notification
 generation

In rxrpc_input_data(), rxrpc_notify_socket() is called if the base sequence
number of the packet is immediately following the hard-ack point at the end
of the function.  However, this isn't sufficient, since the recvmsg side
may have been advancing the window and then overrun the position in which
we're adding - at which point rx_hard_ack >= seq0 and no notification is
generated.

Fix this by always generating a notification at the end of the input
function.

Without this, a long call may stall, possibly indefinitely.

Fixes: 248f219cb8bc ("rxrpc: Rewrite the data and ack handling code")
Signed-off-by: David Howells <dhowells@...hat.com>
---

 net/rxrpc/input.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index 96d54e5bf7bc..ef10fbf71b15 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -599,10 +599,8 @@ static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb)
 				  false, true,
 				  rxrpc_propose_ack_input_data);

-	if (seq0 == READ_ONCE(call->rx_hard_ack) + 1) {
-		trace_rxrpc_notify_socket(call->debug_id, serial);
-		rxrpc_notify_socket(call);
-	}
+	trace_rxrpc_notify_socket(call->debug_id, serial);
+	rxrpc_notify_socket(call);

 unlock:
 	spin_unlock(&call->input_lock);