From 3f99feef88eb867056bd4459e4cf68da33af8861 Mon Sep 17 00:00:00 2001 From: Paolo Valente Date: Sat, 15 Sep 2012 00:41:35 +0000 Subject: [PATCH] pkt_sched: fix virtual-start-time update in QFQ [ Upstream commit 71261956973ba9e0637848a5adb4a5819b4bae83 ] If the old timestamps of a class, say cl, are stale when the class becomes active, then QFQ may assign to cl a much higher start time than the maximum value allowed. This may happen when QFQ assigns to the start time of cl the finish time of a group whose classes are characterized by a higher value of the ratio max_class_pkt/weight_of_the_class with respect to that of cl. Inserting a class with a too high start time into the bucket list corrupts the data structure and may eventually lead to crashes. This patch limits the maximum start time assigned to a class. Signed-off-by: Paolo Valente Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/sched/sch_qfq.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/sched/sch_qfq.c b/net/sched/sch_qfq.c index 103343408593..f86bc727b98f 100644 --- a/net/sched/sch_qfq.c +++ b/net/sched/sch_qfq.c @@ -829,7 +829,10 @@ static void qfq_update_start(struct qfq_sched *q, struct qfq_class *cl) if (mask) { struct qfq_group *next = qfq_ffs(q, mask); if (qfq_gt(roundedF, next->F)) { - cl->S = next->F; + if (qfq_gt(limit, next->F)) + cl->S = next->F; + else /* preserve timestamp correctness */ + cl->S = limit; return; } } -- 2.39.5