Re: [PATCH v2] xfrm: policy: Fix xfrm policy match

From: Yuehaibing <yuehaibing@huawei.com>
To: Xin Long <lucien.xin@gmail.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	davem <davem@davemloft.net>, Jakub Kicinski <kuba@kernel.org>,
	network dev <netdev@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] xfrm: policy: Fix xfrm policy match
Date: Fri, 22 May 2020 20:39:04 +0800	[thread overview]
Message-ID: <1c4c5d40-1e35-f9bb-3f17-01bb4675f3aa@huawei.com> (raw)
In-Reply-To: <CADvbK_cpXOxbWzHzonrzzrrb+Vh3q8NhXnapz0yc9h4H4gN02A@mail.gmail.com>

On 2020/5/22 13:49, Xin Long wrote:
> On Fri, May 22, 2020 at 9:45 AM Yuehaibing <yuehaibing@huawei.com> wrote:
>>
>> On 2020/5/21 14:49, Xin Long wrote:
>>> On Tue, May 19, 2020 at 4:53 PM Steffen Klassert
>>> <steffen.klassert@secunet.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.

Ok, this make sense.

> 
> .
> 