net_sched: red: Avoid devision by zero

BugLink: http://bugs.launchpad.net/bugs/1756866

[ Upstream commit 5c472203 ]

Do not allow delta value to be zero since it is used as a divisor.

Fixes: 8af2a218 ("sch_red: Adaptative RED AQM")
Signed-off-by: Nogah Frankel <nogahf@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

include/net/red.h

@@ -178,7 +178,7 @@ static inline void red_set_parms(struct red_parms *p,
 	p->qth_max	= qth_max << Wlog;
 	p->Wlog		= Wlog;
 	p->Plog		= Plog;
-	if (delta < 0)
+	if (delta <= 0)
 		delta = 1;
 	p->qth_delta	= delta;
 	if (!max_P) {