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sch_cake: Return __NET_XMIT_STOLEN when consuming enqueued skb

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When the GSO splitting feature of sch_cake is enabled, GSO superpackets
will be broken up and the resulting segments enqueued in place of the
original skb. In this case, CAKE calls consume_skb() on the original skb,
but still returns NET_XMIT_SUCCESS. This can confuse parent qdiscs into
assuming the original skb still exists, when it really has been freed. Fix
this by adding the __NET_XMIT_STOLEN flag to the return value in this case.

Fixes: 0c850344d3 ("sch_cake: Conditionally split GSO segments")
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-18231
Link: https://lore.kernel.org/r/20220831092103.442868-1-toke@toke.dk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Toke Høiland-Jørgensen 2022-08-31 11:21:03 +02:00 committed by Jakub Kicinski
parent 5a3a599810
commit 90fabae8a2
1 changed files with 3 additions and 1 deletions
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4
net/sched/sch_cake.c
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@ -1713,6 +1713,7 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch,
}
idx--;
flow = &b->flows[idx];
ret = NET_XMIT_SUCCESS;
/* ensure shaper state isn't stale */
if (!b->tin_backlog) {
@ -1771,6 +1772,7 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch,
qdisc_tree_reduce_backlog(sch, 1-numsegs, len-slen);
consume_skb(skb);
ret |= __NET_XMIT_STOLEN;
} else {
/* not splitting */
cobalt_set_enqueue_time(skb, now);
@ -1904,7 +1906,7 @@ static s32 cake_enqueue(struct sk_buff *skb, struct Qdisc *sch,
}
b->drop_overlimit += dropped;
}
return NET_XMIT_SUCCESS;
return ret;
}
static struct sk_buff *cake_dequeue_one(struct Qdisc *sch)