Subject: Re: [PATCH net 1/3] sched: cls_bpf: fix panic on filter replace

From: John Fastabend <[email-masked]>
Date: Fri, 17 Jul 2015 14:05:09 -0700

On 15-07-17 01:38 PM, Daniel Borkmann wrote:
> The following test case causes a NULL pointer dereference in cls_bpf:
> 
>   FOO="1,6 0 0 4294967295,"
>   tc filter add dev foo parent 1: bpf bytecode "$FOO" flowid 1:1 action ok
>   tc filter replace dev foo parent 1: pref 49152 handle 0x1 \
>             bpf bytecode "$FOO" flowid 1:1 action drop
> 
> The problem is that commit 1f947bf151e9 ("net: sched: rcu'ify cls_bpf")
> accidentally swapped the arguments of list_replace_rcu(), the old
> element needs to be the first argument and the new element the second.
> 
> Fixes: 1f947bf151e9 ("net: sched: rcu'ify cls_bpf")
> Signed-off-by: Daniel Borkmann <[email-masked]>
> ---

Thanks Daniel. Apparently I got this right in cls_basic but botched it
here and in cls_flow.

FWIW,

Acked-by: John Fastabend <[email-masked]>

>  net/sched/cls_bpf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c
> index c79ecfd..e5168f8 100644
> --- a/net/sched/cls_bpf.c
> +++ b/net/sched/cls_bpf.c
> @@ -378,7 +378,7 @@ static int cls_bpf_change(struct net *net, struct sk_buff *in_skb,
>  		goto errout;
>  
>  	if (oldprog) {
> -		list_replace_rcu(&prog->link, &oldprog->link);
> +		list_replace_rcu(&oldprog->link, &prog->link);
>  		tcf_unbind_filter(tp, &oldprog->res);
>  		call_rcu(&oldprog->rcu, __cls_bpf_delete_prog);
>  	} else {
>