[net,1/3] sched: cls_bpf: fix panic on filter replace

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 <daniel@iogearbox.net>
---
 net/sched/cls_bpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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 <daniel@iogearbox.net>
> ---

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

FWIW,

Acked-by: John Fastabend <john.r.fastabend@intel.com>

>  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 {
> 

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On 07/17/2015 11:05 PM, John Fastabend wrote:
...
> Thanks Daniel. Apparently I got this right in cls_basic but botched it
> here and in cls_flow.

Yep, it's correct there. :)

Thanks,
Daniel
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On 7/17/15 2:05 PM, John Fastabend wrote:
> 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<daniel@iogearbox.net>
>> >---
> Thanks Daniel. Apparently I got this right in cls_basic but botched it
> here and in cls_flow.
>
> FWIW,
>
> Acked-by: John Fastabend<john.r.fastabend@intel.com>

Thanks for the quick fix.
Acked-by: Alexei Starovoitov <ast@plumgrid.com>

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