netdev - [PATCH net 5/6] rxrpc: Fix resend event time calculation

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Date:   Tue, 27 Mar 2018 23:44:41 +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 5/6] rxrpc: Fix resend event time calculation

From: Marc Dionne <marc.dionne@...istor.com>

Commit a158bdd3 ("rxrpc: Fix call timeouts") reworked the time calculation
for the next resend event.  For this calculation, "oldest" will be before
"now", so ktime_sub(oldest, now) will yield a negative value.  When passed
to nsecs_to_jiffies which expects an unsigned value, the end result will be
a very large value, and a resend event scheduled far into the future.  This
could cause calls to stall if some packets were lost.

Fix by ordering the arguments to ktime_sub correctly.

Fixes: a158bdd3247b ("rxrpc: Fix call timeouts")
Signed-off-by: Marc Dionne <marc.dionne@...istor.com>
Signed-off-by: David Howells <dhowells@...hat.com>
---

 net/rxrpc/call_event.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c
index 27f77b7d0ead..87ec697ca117 100644
--- a/net/rxrpc/call_event.c
+++ b/net/rxrpc/call_event.c
@@ -225,7 +225,7 @@ static void rxrpc_resend(struct rxrpc_call *call, unsigned long now_j)
 				       ktime_to_ns(ktime_sub(skb->tstamp, max_age)));
 	}

-	resend_at = nsecs_to_jiffies(ktime_to_ns(ktime_sub(oldest, now)));
+	resend_at = nsecs_to_jiffies(ktime_to_ns(ktime_sub(now, oldest)));
 	resend_at += jiffies + rxrpc_resend_timeout;
 	WRITE_ONCE(call->resend_at, resend_at);