[PATCH net] openvswitch: Fix skb leak in IPv6 reassembly.

[PATCH net] openvswitch: Fix skb leak in IPv6 reassembly.

[Daniele Di Proietto]

If nf_ct_frag6_gather() returns an error other than -EINPROGRESS, it
means that we still have a reference to the skb.  We should free it
before returning from handle_fragments, as stated in the comment above.

Fixes: daaa7d647f81 ("netfilter: ipv6: avoid nf_iterate recursion")
CC: Florian Westphal <fw@strlen.de>
CC: Pravin B Shelar <pshelar@ovn.org>
CC: Joe Stringer <joe@ovn.org>
Signed-off-by: Daniele Di Proietto <diproiettod@ovn.org>
---
 net/openvswitch/conntrack.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index 31045ef..fecefa2 100644
--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c
@@ -370,8 +370,11 @@ static int handle_fragments(struct net *net, struct sw_flow_key *key,
 		skb_orphan(skb);
 		memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
 		err = nf_ct_frag6_gather(net, skb, user);
-		if (err)
+		if (err) {
+			if (err != -EINPROGRESS)
+				kfree_skb(skb);
 			return err;
+		}
 
 		key->ip.proto = ipv6_hdr(skb)->nexthdr;
 		ovs_cb.mru = IP6CB(skb)->frag_max_size;
-- 
2.10.2

Re: [PATCH net] openvswitch: Fix skb leak in IPv6 reassembly.

[Eric Dumazet]

On Mon, 2016-11-28 at 15:43 -0800, Daniele Di Proietto wrote:
> If nf_ct_frag6_gather() returns an error other than -EINPROGRESS, it
> means that we still have a reference to the skb.  We should free it
> before returning from handle_fragments, as stated in the comment above.
> 
> Fixes: daaa7d647f81 ("netfilter: ipv6: avoid nf_iterate recursion")
> CC: Florian Westphal <fw@strlen.de>
> CC: Pravin B Shelar <pshelar@ovn.org>
> CC: Joe Stringer <joe@ovn.org>
> Signed-off-by: Daniele Di Proietto <diproiettod@ovn.org>
> ---
>  net/openvswitch/conntrack.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
> index 31045ef..fecefa2 100644
> --- a/net/openvswitch/conntrack.c
> +++ b/net/openvswitch/conntrack.c
> @@ -370,8 +370,11 @@ static int handle_fragments(struct net *net, struct sw_flow_key *key,
>  		skb_orphan(skb);
>  		memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
>  		err = nf_ct_frag6_gather(net, skb, user);
> -		if (err)
> +		if (err) {
> +			if (err != -EINPROGRESS)
> +				kfree_skb(skb);
>  			return err;
> +		}
>  
>  		key->ip.proto = ipv6_hdr(skb)->nexthdr;
>  		ovs_cb.mru = IP6CB(skb)->frag_max_size;

Interesting, have you followed the "GPF in eth_header" thread today ?

In a nutshell, we want a complete patch, not something that would solve
part of the problem.

Re: [PATCH net] openvswitch: Fix skb leak in IPv6 reassembly.

[Florian Westphal]

Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Mon, 2016-11-28 at 15:43 -0800, Daniele Di Proietto wrote:
> > If nf_ct_frag6_gather() returns an error other than -EINPROGRESS, it
> > means that we still have a reference to the skb.  We should free it
> > before returning from handle_fragments, as stated in the comment above.
> > 
> > Fixes: daaa7d647f81 ("netfilter: ipv6: avoid nf_iterate recursion")
> > CC: Florian Westphal <fw@strlen.de>
> > CC: Pravin B Shelar <pshelar@ovn.org>
> > CC: Joe Stringer <joe@ovn.org>
> > Signed-off-by: Daniele Di Proietto <diproiettod@ovn.org>
> > ---
> >  net/openvswitch/conntrack.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
> > index 31045ef..fecefa2 100644
> > --- a/net/openvswitch/conntrack.c
> > +++ b/net/openvswitch/conntrack.c
> > @@ -370,8 +370,11 @@ static int handle_fragments(struct net *net, struct sw_flow_key *key,
> >  		skb_orphan(skb);
> >  		memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
> >  		err = nf_ct_frag6_gather(net, skb, user);
> > -		if (err)
> > +		if (err) {
> > +			if (err != -EINPROGRESS)
> > +				kfree_skb(skb);
> >  			return err;
> > +		}
> >  
> >  		key->ip.proto = ipv6_hdr(skb)->nexthdr;
> >  		ovs_cb.mru = IP6CB(skb)->frag_max_size;
> 
> Interesting, have you followed the "GPF in eth_header" thread today ?
> 
> In a nutshell, we want a complete patch, not something that would solve
> part of the problem.

I think this patch is fine, intent seems to be to only take fully reassembled
skb, rather than a stray fragment (ovs does NOT seem to call handle_fragments
in case skb is already known to not contain a fragment header, afaics).

I'll send a patch for the GPF in eth_header thing soon.

Re: [PATCH net] openvswitch: Fix skb leak in IPv6 reassembly.

[Joe Stringer]

On 28 November 2016 at 16:45, Florian Westphal <fw@strlen.de> wrote:
> Eric Dumazet <eric.dumazet@gmail.com> wrote:
>> On Mon, 2016-11-28 at 15:43 -0800, Daniele Di Proietto wrote:
>> > If nf_ct_frag6_gather() returns an error other than -EINPROGRESS, it
>> > means that we still have a reference to the skb.  We should free it
>> > before returning from handle_fragments, as stated in the comment above.
>> >
>> > Fixes: daaa7d647f81 ("netfilter: ipv6: avoid nf_iterate recursion")
>> > CC: Florian Westphal <fw@strlen.de>
>> > CC: Pravin B Shelar <pshelar@ovn.org>
>> > CC: Joe Stringer <joe@ovn.org>
>> > Signed-off-by: Daniele Di Proietto <diproiettod@ovn.org>
>> > ---
>> >  net/openvswitch/conntrack.c | 5 ++++-
>> >  1 file changed, 4 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
>> > index 31045ef..fecefa2 100644
>> > --- a/net/openvswitch/conntrack.c
>> > +++ b/net/openvswitch/conntrack.c
>> > @@ -370,8 +370,11 @@ static int handle_fragments(struct net *net, struct sw_flow_key *key,
>> >             skb_orphan(skb);
>> >             memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
>> >             err = nf_ct_frag6_gather(net, skb, user);
>> > -           if (err)
>> > +           if (err) {
>> > +                   if (err != -EINPROGRESS)
>> > +                           kfree_skb(skb);
>> >                     return err;
>> > +           }
>> >
>> >             key->ip.proto = ipv6_hdr(skb)->nexthdr;
>> >             ovs_cb.mru = IP6CB(skb)->frag_max_size;
>>
>> Interesting, have you followed the "GPF in eth_header" thread today ?
>>
>> In a nutshell, we want a complete patch, not something that would solve
>> part of the problem.
>
> I think this patch is fine, intent seems to be to only take fully reassembled
> skb, rather than a stray fragment (ovs does NOT seem to call handle_fragments
> in case skb is already known to not contain a fragment header, afaics).

Correct, this is used in OVS only for fragmented packets and this
function either morphs the skb into the full skb fragment chain, or
steals/frees the skb.

> I'll send a patch for the GPF in eth_header thing soon.

Re: [PATCH net] openvswitch: Fix skb leak in IPv6 reassembly.

[Pravin Shelar]

On Mon, Nov 28, 2016 at 3:43 PM, Daniele Di Proietto
<diproiettod@ovn.org> wrote:
> If nf_ct_frag6_gather() returns an error other than -EINPROGRESS, it
> means that we still have a reference to the skb.  We should free it
> before returning from handle_fragments, as stated in the comment above.
>
> Fixes: daaa7d647f81 ("netfilter: ipv6: avoid nf_iterate recursion")
> CC: Florian Westphal <fw@strlen.de>
> CC: Pravin B Shelar <pshelar@ovn.org>
> CC: Joe Stringer <joe@ovn.org>
> Signed-off-by: Daniele Di Proietto <diproiettod@ovn.org>
> ---
>  net/openvswitch/conntrack.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
> index 31045ef..fecefa2 100644
> --- a/net/openvswitch/conntrack.c
> +++ b/net/openvswitch/conntrack.c
> @@ -370,8 +370,11 @@ static int handle_fragments(struct net *net, struct sw_flow_key *key,
>                 skb_orphan(skb);
>                 memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
>                 err = nf_ct_frag6_gather(net, skb, user);
> -               if (err)
> +               if (err) {
> +                       if (err != -EINPROGRESS)
> +                               kfree_skb(skb);
>                         return err;
> +               }
>

This fixes the code. But the patch is adding yet another skb-kfree in
conntrack code. we could simplify it by reusing error handling in
do_execute_actions().
If you think that is too complicated for stable branch, I am fine with
this patch going in as it is.

Re: [PATCH net] openvswitch: Fix skb leak in IPv6 reassembly.

[Pravin Shelar]

On Tue, Nov 29, 2016 at 12:54 AM, Daniele Di Proietto
<diproiettod@ovn.org> wrote:
>
>
> 2016-11-28 23:39 GMT-08:00 Pravin Shelar <pshelar@ovn.org>:
>>
>> On Mon, Nov 28, 2016 at 3:43 PM, Daniele Di Proietto
>> <diproiettod@ovn.org> wrote:
>> > If nf_ct_frag6_gather() returns an error other than -EINPROGRESS, it
>> > means that we still have a reference to the skb.  We should free it
>> > before returning from handle_fragments, as stated in the comment above.
>> >
>> > Fixes: daaa7d647f81 ("netfilter: ipv6: avoid nf_iterate recursion")
>> > CC: Florian Westphal <fw@strlen.de>
>> > CC: Pravin B Shelar <pshelar@ovn.org>
>> > CC: Joe Stringer <joe@ovn.org>
>> > Signed-off-by: Daniele Di Proietto <diproiettod@ovn.org>
>> > ---
>> >  net/openvswitch/conntrack.c | 5 ++++-
>> >  1 file changed, 4 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
>> > index 31045ef..fecefa2 100644
>> > --- a/net/openvswitch/conntrack.c
>> > +++ b/net/openvswitch/conntrack.c
>> > @@ -370,8 +370,11 @@ static int handle_fragments(struct net *net, struct
>> > sw_flow_key *key,
>> >                 skb_orphan(skb);
>> >                 memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
>> >                 err = nf_ct_frag6_gather(net, skb, user);
>> > -               if (err)
>> > +               if (err) {
>> > +                       if (err != -EINPROGRESS)
>> > +                               kfree_skb(skb);
>> >                         return err;
>> > +               }
>> >
>>
>> This fixes the code. But the patch is adding yet another skb-kfree in
>> conntrack code. we could simplify it by reusing error handling in
>> do_execute_actions().
>> If you think that is too complicated for stable branch, I am fine with
>> this patch going in as it is.
>
>
> I thought it was simpler to handle this here rather than changing the
> interface of
> handle_fragments() and ovs_ct_execute(). Also this is more similar to the v4
> case,
> where ip_defrag() frees the skb in case of error.
>
> What do you think?

I agree this is simple enough for stable branch. I will check if ct
action error handling could be simplified bit.

Acked-by: Pravin B Shelar <pshelar@ovn.org>

Re: [PATCH net] openvswitch: Fix skb leak in IPv6 reassembly.

[David Miller]

From: Daniele Di Proietto <diproiettod@ovn.org>
Date: Mon, 28 Nov 2016 15:43:53 -0800

> If nf_ct_frag6_gather() returns an error other than -EINPROGRESS, it
> means that we still have a reference to the skb.  We should free it
> before returning from handle_fragments, as stated in the comment above.
> 
> Fixes: daaa7d647f81 ("netfilter: ipv6: avoid nf_iterate recursion")
> CC: Florian Westphal <fw@strlen.de>
> CC: Pravin B Shelar <pshelar@ovn.org>
> CC: Joe Stringer <joe@ovn.org>
> Signed-off-by: Daniele Di Proietto <diproiettod@ovn.org>

Applied, thanks.