Re: [PATCH] net: sched: fix a use-after-free error on chain on the error exit path

Jiri Pirko
2017-05-20T07:13:19Z

Fri, May 19, 2017 at 07:17:59PM CEST, xiyou.wangcong@gmail.com wrote:
>On Thu, May 18, 2017 at 7:07 AM, Colin King <colin.king@canonical.com> wrote:
>> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
>> index 4020b8d932a1..82ebdc3fcb2e 100644
>> --- a/net/sched/cls_api.c
>> +++ b/net/sched/cls_api.c
>> @@ -511,6 +511,7 @@ static int tc_ctl_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
>> if (n->nlmsg_type == RTM_DELTFILTER && prio == 0) {
>> tfilter_notify_chain(net, skb, n, chain, RTM_DELTFILTER);
>> tcf_chain_destroy(chain);
>
>
>Jiri, how does this work...? An action could hold a refcnt to a filter
>chain, but here you destroy a whole chain without respecting
>the refcnt???

Correct. I missed this. Will fix, thanks.

>
>
>> + chain = NULL;
>> err = 0;
>> goto errout;
>
>Colin, not your fault, I think we may miss something more serious
>when reviewing Jiri's patchset. ;)
>
>Thanks.