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Commit ee09b3c1 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

sfq: fix sfq class stats handling 



sfq_walk() runs without qdisc lock. By the time it selects a non empty
hash slot and sfq_dump_class_stats() is run (with lock held), slot might
have been freed : We then access q->slots[SFQ_EMPTY_SLOT], out of
bounds, and crash in slot_queue_walk()

On previous kernels, bug is here but out of bounds qs[SFQ_DEPTH] and
allot[SFQ_DEPTH] are located in struct sfq_sched_data, so no illegal
memory access happens, only possibly wrong data reported to user.

Also, slot_dequeue_tail() should make sure slot skb chain is correctly
terminated, or sfq_dump_class_stats() can access freed skbs.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 503b1a52

net/sched/sch_sfq.c

+11 −5
Original line number Diff line number Diff line
@@ -281,6 +281,7 @@ static inline struct sk_buff *slot_dequeue_tail(struct sfq_slot *slot) 
	struct sk_buff *skb = slot->skblist_prev;



	slot->skblist_prev = skb->prev;

	skb->prev->next = (struct sk_buff *)slot;

	skb->next = skb->prev = NULL;

	return skb;

}
@@ -608,14 +609,19 @@ static int sfq_dump_class_stats(struct Qdisc *sch, unsigned long cl, 
				struct gnet_dump *d)

{

	struct sfq_sched_data *q = qdisc_priv(sch);

	const struct sfq_slot *slot = &q->slots[q->ht[cl - 1]];

	struct gnet_stats_queue qs = { .qlen = slot->qlen };

	struct tc_sfq_xstats xstats = { .allot = slot->allot };

	sfq_index idx = q->ht[cl - 1];

	struct gnet_stats_queue qs = { 0 };

	struct tc_sfq_xstats xstats = { 0 };

	struct sk_buff *skb;



	if (idx != SFQ_EMPTY_SLOT) {

		const struct sfq_slot *slot = &q->slots[idx];



		xstats.allot = slot->allot;

		qs.qlen = slot->qlen;

		slot_queue_walk(slot, skb)

			qs.backlog += qdisc_pkt_len(skb);



	}

	if (gnet_stats_copy_queue(d, &qs) < 0)

		return -1;

	return gnet_stats_copy_app(d, &xstats, sizeof(xstats));