netdev - Re: [PATCH bpf-next 2/2] netkit: use netlink policy for mode and policy attributes validation

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Message-ID: <36072f45-0d42-7284-d0dc-295f543fe40f@blackwall.org>
Date: Thu, 26 Oct 2023 17:23:27 +0300
From: Nikolay Aleksandrov <razor@...ckwall.org>
To: Ido Schimmel <idosch@...sch.org>
Cc: bpf@...r.kernel.org, jiri@...nulli.us, netdev@...r.kernel.org,
 martin.lau@...ux.dev, ast@...nel.org, andrii@...nel.org,
 john.fastabend@...il.com, kuba@...nel.org, andrew@...n.ch, toke@...nel.org,
 toke@...hat.com, sdf@...gle.com, daniel@...earbox.net
Subject: Re: [PATCH bpf-next 2/2] netkit: use netlink policy for mode and
 policy attributes validation

On 10/26/23 17:11, Ido Schimmel wrote:
> On Thu, Oct 26, 2023 at 12:41:06PM +0300, Nikolay Aleksandrov wrote:
>>   static const struct nla_policy netkit_policy[IFLA_NETKIT_MAX + 1] = {
>>   	[IFLA_NETKIT_PEER_INFO]		= { .len = sizeof(struct ifinfomsg) },
>> -	[IFLA_NETKIT_POLICY]		= { .type = NLA_U32 },
>> -	[IFLA_NETKIT_MODE]		= { .type = NLA_U32 },
>> -	[IFLA_NETKIT_PEER_POLICY]	= { .type = NLA_U32 },
>> +	[IFLA_NETKIT_POLICY]		= NLA_POLICY_VALIDATE_FN(NLA_U32,
>> +								 netkit_check_policy),
> 
> Nik, it's problematic to use NLA_POLICY_VALIDATE_FN() with anything
> other than NLA_BINARY. See commit 9e17f99220d1 ("net/sched: act_mpls:
> Fix warning during failed attribute validation").
> 

But how is that code called at all? The validation type is 
NLA_VALIDATE_FUNCTION(), not NLA_VALIDATE_MIN/MAX/RANGE/RANGE_WARN...
nla_validate_int_range() is called only on:
         case NLA_VALIDATE_RANGE_PTR:
         case NLA_VALIDATE_RANGE:
         case NLA_VALIDATE_RANGE_WARN_TOO_LONG:
         case NLA_VALIDATE_MIN:
         case NLA_VALIDATE_MAX:

Anyway, I'll switch to NLA_BINARY in a bit to make sure it's ok. Thanks 
for the pointer.

>> +	[IFLA_NETKIT_MODE]		= NLA_POLICY_VALIDATE_FN(NLA_U32,
>> +								 netkit_check_mode),
>> +	[IFLA_NETKIT_PEER_POLICY]	= NLA_POLICY_VALIDATE_FN(NLA_U32,
>> +								 netkit_check_policy),
>>   	[IFLA_NETKIT_PRIMARY]		= { .type = NLA_REJECT,
>>   					    .reject_message = "Primary attribute is read-only" },
>>   };
>> -- 
>> 2.38.1
>>
>>