pkt_sched: fix virtual-start-time update in QFQ
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 <paolo.valente@unimore.it> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -865,7 +865,10 @@ static void qfq_update_start(struct qfq_sched *q, struct qfq_class *cl)
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if (mask) {
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struct qfq_group *next = qfq_ffs(q, mask);
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if (qfq_gt(roundedF, next->F)) {
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cl->S = next->F;
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if (qfq_gt(limit, next->F))
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cl->S = next->F;
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else /* preserve timestamp correctness */
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cl->S = limit;
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return;
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}
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}
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