From 89e1df74f841fc31e81838d30594c4eff01859f8 Mon Sep 17 00:00:00 2001 From: Guillaume Chazarain Date: Fri, 21 Jul 2006 14:45:25 -0700 Subject: [PATCH] [PKT_SCHED] netem: Fix slab corruption with netem (2nd try) CONFIG_DEBUG_SLAB found the following bug: netem_enqueue() in sch_netem.c gets a pointer inside a slab object: struct netem_skb_cb *cb = (struct netem_skb_cb *)skb->cb; But then, the slab object may be freed: skb = skb_unshare(skb, GFP_ATOMIC) cb is still pointing inside the freed skb, so here is a patch to initialize cb later, and make it clear that initializing it sooner is a bad idea. [From Stephen Hemminger: leave cb unitialized in order to let gcc complain in case of use before initialization] Signed-off-by: Guillaume Chazarain Signed-off-by: David S. Miller --- net/sched/sch_netem.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index c5bd8064e6d..a08ec4c7c55 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -148,7 +148,8 @@ static long tabledist(unsigned long mu, long sigma, static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch) { struct netem_sched_data *q = qdisc_priv(sch); - struct netem_skb_cb *cb = (struct netem_skb_cb *)skb->cb; + /* We don't fill cb now as skb_unshare() may invalidate it */ + struct netem_skb_cb *cb; struct sk_buff *skb2; int ret; int count = 1; @@ -200,6 +201,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch) skb->data[net_random() % skb_headlen(skb)] ^= 1<<(net_random() % 8); } + cb = (struct netem_skb_cb *)skb->cb; if (q->gap == 0 /* not doing reordering */ || q->counter < q->gap /* inside last reordering gap */ || q->reorder < get_crandom(&q->reorder_cor)) { -- 2.20.1