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net: sched: fix use-after-free in tcf_action_destroy and tcf_del_walker 

Recent commit d7fb60b9ca ("net_sched: get rid of tcfa_rcu") removed
freeing in call_rcu, which changed already existing hard-to-hit
race condition into 100% hit:

[  598.599825] BUG: unable to handle kernel NULL pointer dereference at 0000000000000030
[  598.607782] IP: tcf_action_destroy+0xc0/0x140

Or:

[   40.858924] BUG: unable to handle kernel NULL pointer dereference at 0000000000000030
[   40.862840] IP: tcf_generic_walker+0x534/0x820

Fix this by storing the ops and use them directly for module_put call.

Fixes: a85a970af2 ("net_sched: move tc_action into tcf_common")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jiri Pirko 2017-09-13 17:32:37 +02:00 committed by David S. Miller
parent 822f8565c9
commit 255cd50f20
1 changed files with 4 additions and 2 deletions
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6
net/sched/act_api.c
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@ -180,7 +180,7 @@ static int tcf_del_walker(struct tcf_idrinfo *idrinfo, struct sk_buff *skb,
idr_for_each_entry_ext(idr, p, id) {
ret = __tcf_idr_release(p, false, true);
if (ret == ACT_P_DELETED) {
module_put(p->ops->owner);
module_put(ops->owner);
n_i++;
} else if (ret < 0) {
goto nla_put_failure;
@ -514,13 +514,15 @@ EXPORT_SYMBOL(tcf_action_exec);
int tcf_action_destroy(struct list_head *actions, int bind)
{
const struct tc_action_ops *ops;
struct tc_action *a, *tmp;
int ret = 0;
list_for_each_entry_safe(a, tmp, actions, list) {
ops = a->ops;
ret = __tcf_idr_release(a, bind, true);
if (ret == ACT_P_DELETED)
module_put(a->ops->owner);
module_put(ops->owner);
else if (ret < 0)
return ret;
}