netdev - Re: [RFC PATCH v4 01/19] landlock: Support socket access-control

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Message-ID: <965372d6-85e7-06e2-624f-192b7a492d0e@huawei-partners.com>
Date: Sat, 22 Nov 2025 19:51:17 +0300
From: Mikhail Ivanov <ivanov.mikhail1@...wei-partners.com>
To: Günther Noack <gnoack3000@...il.com>, <mic@...ikod.net>
CC: <gnoack@...gle.com>, <willemdebruijn.kernel@...il.com>,
	<matthieu@...fet.re>, <linux-security-module@...r.kernel.org>,
	<netdev@...r.kernel.org>, <netfilter-devel@...r.kernel.org>,
	<yusongping@...wei.com>, <artem.kuzin@...wei.com>,
	<konstantin.meskhidze@...wei.com>
Subject: Re: [RFC PATCH v4 01/19] landlock: Support socket access-control

On 11/22/2025 3:18 PM, Günther Noack wrote:
> On Sat, Nov 22, 2025 at 02:13:08PM +0300, Mikhail Ivanov wrote:
>> On 11/22/2025 1:49 PM, Günther Noack wrote:
>>> (Remark, should those be exposed as constants?)
>>
>> I thought it could overcomplicate socket rules definition and Landlock
>> API. Do you think introducing such constants will be better decision?
> 
> No, I am not convinced either.  FWIW, there is a bit of prior art for
> "wildcard-like" -1 constants (grepping include/uapi for 'define.*-1'),
> but then again, the places where people did the opposite are hard to
> grep for.  I would also be OK if we documented "-1" in that place and
> left out the constant.
> 
> Mickaël, maybe you have a preference for the API style here?
> 
> 
>>>> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
>>>> index 33eafb71e4f3..e9f500f97c86 100644
>>>> --- a/security/landlock/syscalls.c
>>>> +++ b/security/landlock/syscalls.c
>>>> @@ -407,6 +458,8 @@ static int add_rule_net_port(struct landlock_ruleset *ruleset,
>>>>     *   &landlock_net_port_attr.allowed_access is not a subset of the ruleset
>>>>     *   handled accesses)
>>>>     * - %EINVAL: &landlock_net_port_attr.port is greater than 65535;
>>>> + * - %EINVAL: &landlock_socket_attr.{family, type} are greater than 254 or
>>>> + *   &landlock_socket_attr.protocol is greater than 65534;
>>>
>>> Hmm, this is a bit annoying that these values have such unusual
>>> bounds, even though the input parameters are 32 bit.  We are exposing
>>> a little bit that we are internally storing this with only 8 and 16
>>> bits...  (I don't know a better solution immediately either, though. I
>>> think we discussed this on a previous version of the patch set as well
>>> and ended up with permitting larger values than the narrower SOCK_MAX
>>> etc bounds.)
>>
>> I agree, one of the possible solutions may be to store larger values in
>> socket keys (eg. s32), but this would require to make a separate
>> interface for storing socket rules (in order to not change key size for
>> other type of rules which is currently 32-64 bit depending on virtual
>> address size).
> 
> Yes, I'd be OK with it.
> 
> Do I remember this correctly that we settled on enforcing the looser
> UINT8_MAX and UINT16_MAX instead of SOCK_MAX, AF_MAX, which we used in
> v3 and before?  I tried to find the conversation but could not find it
> any more.  (Or did you have other reasons why you switched the
> implementation to use these larger bounds?)

Mickaël mentioned that Landlock should accept rules defined even for
unsupported protocol families:
https://lore.kernel.org/all/20241128.um9voo5Woo3I@digikod.net/

> 
> Thanks,
> –Günther