[PATCH v6 bpf-next 3/4] bpf: add bpf_init_inode_xattr kfunc for atomic inode labeling

[Kumar Kartikeya Dwivedi]

On Fri Jul 31, 2026 at 9:05 PM CEST, Paul Moore wrote:
> On Fri, Jul 31, 2026 at 2:50 PM Kumar Kartikeya Dwivedi
> <memxor at gmail.com> wrote:
>> On Fri Jul 31, 2026 at 8:42 PM CEST, Paul Moore wrote:
>> > On Fri, Jul 31, 2026 at 2:18 PM Kumar Kartikeya Dwivedi
>> > <memxor at gmail.com> wrote:
>> >> On Fri Jul 31, 2026 at 6:59 PM CEST, Paul Moore wrote:
>> >> > On Fri, Jul 31, 2026 at 12:32 PM Kumar Kartikeya Dwivedi
>> >> > <memxor at gmail.com> wrote:
>> >> >> On Fri Jul 31, 2026 at 6:02 PM CEST, Paul Moore wrote:
>> >> >> > On Fri, Jul 31, 2026 at 11:44 AM Kumar Kartikeya Dwivedi
>> >> >> > <memxor at gmail.com> wrote:
>> >> >> >> On Fri Jul 31, 2026 at 5:30 PM CEST, David Windsor wrote:
>> >> >> >> > On Fri, Jul 31, 2026 at 11:17 AM Paul Moore <paul at paul-moore.com> wrote:
>> >
>> > ...
>> >
>> >> Yes, I understand you feel it should be placed under security/. You are entitled
>> >> to your opinion.
>> >>
>> >> No, I do not think the newly added kfunc is a big enough layering violation such
>> >> that we need to do it ASAP, disregarding everything else outlined above. I am
>> >> sure you see that too. There are several other instances of similar kfuncs.
>> >>
>> >> Therefore, please attempt to meet me halfway here.
>> >
>> > I'm happy to work with you, and/or anyone else, who wants to work on
>> > finding a way to test kfuncs that live in security/bpf_lsm_kfuncs.c.
>>
>> Right, and for that file to exist, you need to get everyone (FS, BPF folks) to
>> agree on whether placing all such kfuncs there makes sense. It is not for both
>> of us to decide on our own. So let's revisit this whole topic once you've done
>> that exercise.
>
> The kfunc that David has proposed must be located in
> security/bpf_lsm_kfuncs.c, similar to the VFS kfuncs and
> fs/bpf_fs_kfuncs.c.  If you read David's bpf_init_inode_xattr() kfunc

Sigh.

I now went and read the archives, and Christian already told you no before [0],
which I missed in my first read. So two people whom this code affects already
objected to your proposal.

  [0]: https://lore.kernel.org/bpf/20260625-schnabel-rennmaschine-parieren-bcb352c3cf59@brauner

> you will notice there is nothing in the function relating to the VFS,
> well other than the "inode" and "xattr" in the name of the function;

I can also read it the other way. There is only one "security_lsmxattr_add()"
call that is LSM related, and the rest is VFS or BPF specific stuff.

There would be no xattr support in LSM code without filesystems implementing
them.

Please avoid making absurd and non-sensical arguments.

If we went by this logic, we would have to move the entirety of the kernel under
security/, since anything that calls into LSM code becomes eligible to go there.

> this is purely a LSM kfunc and I stand by my previous comments.  The
> BPF maintainers have seen fit to decide quite a few things LSM related
> solely on their own, I see no reason why requiring a LSM kfunc be
> located in security/bpf_lsm_kfuncs.c is unreasonable given our current
> situation.
>
> As I said earlier, I'm happy to work with you, David, or anyone else
> on ensuring security/bpf_lsm_kfuncs.c has the proper test coverage,
> but I'm not going to continue to go back and forth about the location
> of the bpf_init_inode_xattr() kfunc that is proposed in this patchset.
> If you, or any of the other BPF maintainers, are not able to live with
> that location then David will need to find another way.

Yeah, I think we've spilled enough ink on this. We'll figure out a way to move
things forward.  Since VFS people disagree too, the kfunc should stay where it
is in this series.

I am always open to revisiting all this once you can convince others by making
useful arguments, instead of imposing your will onto them and throwing a tantrum.