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: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
index 13322e8..6a2f88f 100644
--- a/net/sched/sch_sfq.c
+++ b/net/sched/sch_sfq.c
@@ -281,6 +281,7 @@
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 @@
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));