sctp: don't compare hb_timer expire date before starting it

Maciej Kwiecien · davem330 · commit d1f20c03f481 · 2019-02-22T11:11:54.000-08:00
hb_timer might not start at all for a particular transport because its start is conditional. In a result a node is not sending heartbeats. Function sctp_transport_reset_hb_timer has two roles: - initial start of hb_timer for a given transport, - update expire date of hb_timer for a given transport. The function is optimized to update timer's expire only if it is before a new calculated one but this comparison is invalid for a timer which has not yet started. Such a timer has expire == 0 and if a new expire value is bigger than (MAX_JIFFIES / 2 + 2) then "time_before" macro will fail and timer will not start resulting in no heartbeat packets send by the node. This was found when association was initialized within first 5 mins after system boot due to jiffies init value which is near to MAX_JIFFIES. Test kernel version: 4.9.154 (ARCH=arm) hb_timer.expire = 0; //initialized, not started timer new_expire = MAX_JIFFIES / 2 + 2; //or more time_before(hb_timer.expire, new_expire) == false Fixes: ba6f5e3 ("sctp: avoid refreshing heartbeat timer too often") Reported-by: Marcin Stojek <marcin.stojek@nokia.com> Tested-by: Marcin Stojek <marcin.stojek@nokia.com> Signed-off-by: Maciej Kwiecien <maciej.kwiecien@nokia.com> Reviewed-by: Alexander Sverdlin <alexander.sverdlin@nokia.com> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
@@ -207,7 +207,8 @@ void sctp_transport_reset_hb_timer(struct sctp_transport *transport)
 
 	/* When a data chunk is sent, reset the heartbeat interval.  */
 	expires = jiffies + sctp_transport_timeout(transport);
-	if (time_before(transport->hb_timer.expires, expires) &&
+	if ((time_before(transport->hb_timer.expires, expires) ||
+	     !timer_pending(&transport->hb_timer)) &&
 	    !mod_timer(&transport->hb_timer,
 		       expires + prandom_u32_max(transport->rto)))
 		sctp_transport_hold(transport);
