From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jamal Hadi Salim <jhs@mojatatu.com>
Subject: Re: [PATCH net-next v11 3/4] net sched actions: dump more than
 TCA_ACT_MAX_PRIO actions per batch
Date: Fri, 28 Jul 2017 09:41:44 -0400
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Cc: davem@davemloft.net, netdev@vger.kernel.org,
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To: Jiri Pirko <jiri@resnulli.us>
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On 17-07-25 08:37 AM, Jiri Pirko wrote:
> Tue, Jul 25, 2017 at 02:34:58PM CEST, jhs@mojatatu.com wrote:
>> On 17-07-25 07:33 AM, Jiri Pirko wrote:
>>> Tue, Jul 25, 2017 at 01:22:44PM CEST, jhs@mojatatu.com wrote:

[..]
>>> What if I pass val 0x1 and selector 0x0 from userspace. I don't have the
>>> bit selected, so you should not process it in kernel, no?
>>>
>>
>> Yes, valid point. I am not sure - should we reject?
> 
> I think that the validation might check this and reject. Makes sense to
> me.
> 

How does this look? I havent tested it but covers all angles
I can think of.

static int validate_nla_bitfield32(const struct nlattr *nla,
                                     void *valid_flags_allowed)
{
         const struct nla_bitfield32 *bf = nla_data(nla);
         u32 *valid_flags_mask = valid_flags_allowed;

         if (!valid_flags_allowed)
                 return -EINVAL;
         /*disallow invalid selector */
         if ((bf->selector & valid_flags_allowed) >*valid_flags_allowed)
                 return -EINVAL;
         /*disallow invalid bit values */
         if (bf->value & ~*valid_flags_mask)
                 return -EINVAL;
         /*disallow valid bit values that are not selected*/
         if (bf->value & ~nbf->selector)
                 return -EINVAL;

         return 0;
}

cheers,
jamal