Re: [PATCH bpf-next 4/8] bpf, lsm: Let BPF LSM provide xattrs at inode creation

[Justin Suess]

On Thu, Sep 24, 2026 at 12:23:13PM -0400, Paul Moore wrote:
> On Thu, Sep 24, 2026 at 12:15 PM Justin Suess <utilityemal77@xxxxxxxxx> wrote:
> > On Wed, Sep 23, 2026 at 03:14:28PM -0400, David Windsor wrote:
> > > On Wed, Sep 23, 2026 at 12:57 PM Paul Moore <paul@xxxxxxxxxxxxxx> wrote:
> > > > @David, simply for my own understanding, did you ask Daniel to do
> > > > this, or was Daniel operating on his own with this patchset?
> > > >
> > >
> > > Daniel and I work together and both have things written on top of this
> > > kfunc. He reached out to collaborate, I agreed. We're also going to
> > > send bpf_set_file_xattr shortly.
> > >
> > > This implementation was chosen due to its immediate mergeability (it
> > > only touches security/bpf), but was actually suggested by Kumar in v1
> > > or so of my original series.
> > >
> > > That said, sorry for any confusion about this appearing as a new
> > > series rather than as v7 of my previous one.
> >
> > Howdy all,
> >
> > Hope you all are doing well and having a good Thursday.
> >
> > These patches are excellent and useful, and have been in the pipeline
> > for a while.
> >
> > In the interest of moving forward:
> >
> > Would you both be able to live with the following: provide a security hook
> > for lsm_get_xattr_slot or another proper interface with the necessary
> > abstraction, and keep the kfunc where it is in fs/?
> 
> That still doesn't change the fundamentals around the kfunc: it is
> really only a valid to call it from within the LSM inode_init_security
> callback, it populates a LSM framework managed buffer, and that buffer
> is then used to by the LSM framework code in
> security_inode_init_security() to do the xattr initialization using
> the values from the BPF LSM as well as all of the other configured
> LSMs.  It's very hard to see this as anything other than an LSM kfunc.
> I worked with David over several revisions of his patchset to review
> the code and get it in a good place, I'm supportive of the basic
> ideas, but this really needs to be located in
> security/bpf_lsm_kfuncs.c as it is an LSM kfunc.  As we've seen there
> is precedence for subsystem specific kfuncs located in the associated
> subsystem's directory, things should be no different here.
>
Hello,

I'm less arguing for any particular placement:

More so that the concrete security interest of just getting the kfunc
*somewhere* is much more important. I have no doubt that the function
would be equally well stewarded in either directory.

The xattr kfunc in security/ question can be fought best in a different
venue where it's not holding back good contributions. So I think
swallowing this bitter pill for now will be best for cooperation and
good faith if nothing else, otherwise users and contributors are left
footing the bill indefinitely.

Admittedly I'm biased and am toying with a project that this kfunc
would be really nice in, so take me with a grain of salt :)

Thanks,
Justin

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