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]
Thanks.
--
Guillaume
Signed-off-by: Guillaume Chazarain <[EMAIL PROTECTED]>
---
net/sched/sch_netem.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff -r 1b8d63e34819 net/sched/sch_netem.c
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -148,7 +148,8 @@ static int netem_enqueue(struct sk_buff
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->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)) {
