netdev - Re: [PATCH net] net/sched: act_mpls: ensure LSE is pullable before reading it

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Message-ID: <be2382dca0d817a4b5ac5b9820307ec82ce30c96.camel@redhat.com>
Date:   Wed, 18 Nov 2020 18:07:22 +0100
From:   Davide Caratti <dcaratti@...hat.com>
To:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org,
        Jakub Kicinski <kuba@...nel.org>, gnault@...hat.com
Subject: Re: [PATCH net] net/sched: act_mpls: ensure LSE is pullable before
 reading it

On Wed, 2020-11-18 at 13:47 -0300, Marcelo Ricardo Leitner wrote:
> On Wed, Nov 18, 2020 at 05:36:52PM +0100, Davide Caratti wrote:
> 
> Hi,
> 
> >  	case TCA_MPLS_ACT_MODIFY:
> > +		if (!pskb_may_pull(skb,
> > +				   skb_network_offset(skb) + sizeof(new_lse)))
> > +			goto drop;
> >  		new_lse = tcf_mpls_get_lse(mpls_hdr(skb), p, false);
> >  		if (skb_mpls_update_lse(skb, new_lse))
> >  			goto drop;
> 
> Seems TCA_MPLS_ACT_DEC_TTL is also affected. skb_mpls_dec_ttl() will
> also call mpls_hdr(skb) without this check.
> 
>   Marcelo
> 
... yes, correct; and at a first glance, also set_mpls() in
openvswitch/action.c has the same (theoretical) issue. I will follow-up
with other 2 patches, ok?

thanks!
-- 
davide