linux-kernel - Re: [PATCH v2] xfrm: policy: Fix xfrm policy match

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Message-ID: <CADvbK_cpXOxbWzHzonrzzrrb+Vh3q8NhXnapz0yc9h4H4gN02A@mail.gmail.com>
Date:   Fri, 22 May 2020 13:49:05 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     Yuehaibing <yuehaibing@...wei.com>
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        davem <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
        network dev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] xfrm: policy: Fix xfrm policy match

On Fri, May 22, 2020 at 9:45 AM Yuehaibing <yuehaibing@...wei.com> wrote:
>
> On 2020/5/21 14:49, Xin Long wrote:
> > On Tue, May 19, 2020 at 4:53 PM Steffen Klassert
> > <steffen.klassert@...unet.com> wrote:
> >>
> >> On Fri, May 15, 2020 at 04:39:57PM +0800, Yuehaibing wrote:
> >>>
> >>> Friendly ping...
> >>>
> >>> Any plan for this issue?
> >>
> >> There was still no consensus between you and Xin on how
> >> to fix this issue. Once this happens, I consider applying
> >> a fix.
> >>
> > Sorry, Yuehaibing, I can't really accept to do: (A->mark.m & A->mark.v)
> > I'm thinking to change to:
> >
> >  static bool xfrm_policy_mark_match(struct xfrm_policy *policy,
> >                                    struct xfrm_policy *pol)
> >  {
> > -       u32 mark = policy->mark.v & policy->mark.m;
> > -
> > -       if (policy->mark.v == pol->mark.v && policy->mark.m == pol->mark.m)
> > -               return true;
> > -
> > -       if ((mark & pol->mark.m) == pol->mark.v &&
> > -           policy->priority == pol->priority)
> > +       if (policy->mark.v == pol->mark.v &&
> > +           (policy->mark.m == pol->mark.m ||
> > +            policy->priority == pol->priority))
> >                 return true;
> >
> >         return false;
> >
> > which means we consider (the same value and mask) or
> > (the same value and priority) as the same one. This will
> > cover both problems.
>
>   policy A (mark.v = 0x1011, mark.m = 0x1011, priority = 1)
>   policy B (mark.v = 0x1001, mark.m = 0x1001, priority = 1)
I'd think these are 2 different policies.

>
>   when fl->flowi_mark == 0x12341011, in xfrm_policy_match() do check like this:
>
>         (fl->flowi_mark & pol->mark.m) != pol->mark.v
>
>         0x12341011 & 0x1011 == 0x00001011
>         0x12341011 & 0x1001 == 0x00001001
>
>  This also match different policy depends on the order of policy inserting.
Yes, this may happen when a user adds 2  policies like that.
But I think this's a problem that the user doesn't configure it well,
'priority' should be set.
and this can not be avoided, also such as:

   policy A (mark.v = 0xff00, mark.m = 0x1000, priority = 1)
   policy B (mark.v = 0x00ff, mark.m = 0x0011, priority = 1)

   try with 0x12341011

So just be it, let users decide.