net: sched: Fix use after free in red_enqueue()

We can't use "skb" again after passing it to qdisc_enqueue().  This is
basically identical to commit 2f09707d0c97 ("sch_sfb: Also store skb
len before calling child enqueue").

Fixes: d7f4f332f082 ("sch_red: update backlog as well")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_red.c b/net/sched/sch_red.c
index a5a401f..9812932 100644 (file)
--- a/net/sched/sch_red.c
+++ b/net/sched/sch_red.c
@@ -72,6 +72,7 @@ static int red_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 {
        struct red_sched_data *q = qdisc_priv(sch);
        struct Qdisc *child = q->qdisc;
+       unsigned int len;
        int ret;
 
        q->vars.qavg = red_calc_qavg(&q->parms,
@@ -126,9 +127,10 @@ static int red_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                break;
        }
 
+       len = qdisc_pkt_len(skb);
        ret = qdisc_enqueue(skb, child, to_free);
        if (likely(ret == NET_XMIT_SUCCESS)) {
-               qdisc_qstats_backlog_inc(sch, skb);
+               sch->qstats.backlog += len;
                sch->q.qlen++;
        } else if (net_xmit_drop_count(ret)) {
                q->stats.pdrop++;