Commit 89e1df74 authored by Guillaume Chazarain's avatar Guillaume Chazarain Committed by David S. Miller

[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: default avatarGuillaume Chazarain <guichaz@yahoo.fr>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fbeff3c1
...@@ -148,7 +148,8 @@ static long tabledist(unsigned long mu, long sigma, ...@@ -148,7 +148,8 @@ static long tabledist(unsigned long mu, long sigma,
static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch) static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
{ {
struct netem_sched_data *q = qdisc_priv(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; struct sk_buff *skb2;
int ret; int ret;
int count = 1; int count = 1;
...@@ -200,6 +201,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch) ...@@ -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); 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 */ if (q->gap == 0 /* not doing reordering */
|| q->counter < q->gap /* inside last reordering gap */ || q->counter < q->gap /* inside last reordering gap */
|| q->reorder < get_crandom(&q->reorder_cor)) { || q->reorder < get_crandom(&q->reorder_cor)) {
......
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