From: Toke Høiland-Jørgensen toke@toke.dk
[ Upstream commit 9efd23297cca530bb35e1848665805d3fcdd7889 ]
The sch_sfb enqueue() routine assumes the skb is still alive after it has been enqueued into a child qdisc, using the data in the skb cb field in the increment_qlen() routine after enqueue. However, the skb may in fact have been freed, causing a use-after-free in this case. In particular, this happens if sch_cake is used as a child of sfb, and the GSO splitting mode of CAKE is enabled (in which case the skb will be split into segments and the original skb freed).
Fix this by copying the sfb cb data to the stack before enqueueing the skb, and using this stack copy in increment_qlen() instead of the skb pointer itself.
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-18231 Fixes: e13e02a3c68d ("net_sched: SFB flow scheduler") Signed-off-by: Toke Høiland-Jørgensen toke@toke.dk Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/sched/sch_sfb.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/net/sched/sch_sfb.c b/net/sched/sch_sfb.c index da047a37a3bf3..f180cf95cfc97 100644 --- a/net/sched/sch_sfb.c +++ b/net/sched/sch_sfb.c @@ -135,15 +135,15 @@ static void increment_one_qlen(u32 sfbhash, u32 slot, struct sfb_sched_data *q) } }
-static void increment_qlen(const struct sk_buff *skb, struct sfb_sched_data *q) +static void increment_qlen(const struct sfb_skb_cb *cb, struct sfb_sched_data *q) { u32 sfbhash;
- sfbhash = sfb_hash(skb, 0); + sfbhash = cb->hashes[0]; if (sfbhash) increment_one_qlen(sfbhash, 0, q);
- sfbhash = sfb_hash(skb, 1); + sfbhash = cb->hashes[1]; if (sfbhash) increment_one_qlen(sfbhash, 1, q); } @@ -283,6 +283,7 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sfb_sched_data *q = qdisc_priv(sch); struct Qdisc *child = q->qdisc; struct tcf_proto *fl; + struct sfb_skb_cb cb; int i; u32 p_min = ~0; u32 minqlen = ~0; @@ -399,11 +400,12 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch, }
enqueue: + memcpy(&cb, sfb_skb_cb(skb), sizeof(cb)); ret = qdisc_enqueue(skb, child, to_free); if (likely(ret == NET_XMIT_SUCCESS)) { qdisc_qstats_backlog_inc(sch, skb); sch->q.qlen++; - increment_qlen(skb, q); + increment_qlen(&cb, q); } else if (net_xmit_drop_count(ret)) { q->stats.childdrop++; qdisc_qstats_drop(sch);