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sfq: fix sfq class stats handling

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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: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2010-12-22 11:39:59 -08:00 committed by David S. Miller
parent 503b1a529a
commit ee09b3c1cf
1 changed files with 11 additions and 5 deletions
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16
net/sched/sch_sfq.c
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@ -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;
slot_queue_walk(slot, skb)
qs.backlog += qdisc_pkt_len(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));