LSM stacking in next for 6.1?

[Casey Schaufler]

On 10/30/2022 9:37 AM, Kees Cook wrote:
> On October 30, 2022 7:02:52 AM PDT, Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp> wrote:
>> Casey's patchset is trying to provide LSM ID Repository for userspace programs.
>> But an LSM ID value cannot be assigned to that LSM unless that module is
>> available in the upstream kernel. This means that, developers are not allowed
>> to develop a new LSM module even with the intention to become available in the
>> upstream kernel, for there always is a risk of LSM ID collision which the LSM ID
>> Repository should have avoided from the beginning. Also, this means that, unlike
>> PCI devices, users are not allowed to use out-of-tree LSM modules which have to
>> remain out-of-tree due to proposed-but-not-accepted by the upstream kernel.
>> This is a serious bug; is LSM a proprietary/closed code where modification is
>> impossible due to an End-User License Agreement?
> You are way off in the weeds with false equivalencies.
>
>> You have only three choices:
>>
>>  (1) allow assigning LSM ID integer value to all LSM modules (regardless of
>>      whether that module was merged into upstream kernel)
> We are not hardware manufacturers.
>
>>  (2) use module name string value as LSM ID
> This results is greater code complexity. If you see a way to do this, send a patch. Instead of unhelpfully saying "no, do it differently", show a solution.
>
>>  (3) dynamically assign LSM ID integer value when an LSM module is registered
> Again, send a patch.
>
>> There never is fourth choice:
>>
>>  (4) assigning LSM ID integer value to only LSM modules which were merged
>>      into upstream kernel
>>
>> The fourth choice is complete lockout of out of tree projects.
> This is just not a real outcome. How is this any different from syscalls, capability bits, prctl values, ELF flags, etc?
>
Loadability and the LSM ID are completely separate issues. Show me a patch
that implements loading modules and I will show you how to change it to
accommodate the LSM ID. That is, if it isn't obvious at that point.