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[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 <guichaz@yahoo.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Guillaume Chazarain 2006-07-21 14:45:25 -07:00 committed by David S. Miller
parent fbeff3c1d3
commit 89e1df74f8
1 changed files with 3 additions and 1 deletions
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4
net/sched/sch_netem.c
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@ -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)) {