Re: [PATCH v3 bpf-next 0/6] Enable writing xattr from BPF programs

Andrii Nakryiko
2024-12-12T19:39:17Z

On Wed, Dec 11, 2024 at 5:18 AM Theodore Ts'o <tytso@mit.edu> wrote:
>
> On Tue, Dec 10, 2024 at 02:06:21PM -0800, Song Liu wrote:
> > Add support to set and remove xattr from BPF program. Also add
> > security.bpf. xattr name prefix.
>
> If the system allows for the execution of unprivileged BPF programs
> (e.g., ones where a random user can load their own BPF programs), will
> they have hte ability to set and remove security.bpf.* xattrs? If the
> answer is yes, should this be disallowed?

It's not 100% clear from Song's reply, but the answer is "no". You
can't use this from unprivileged BPF programs (BPF LSM is privileged
and requires root, effectively).

>
> I note that one of the use cases seems to be BPF-based LSM's, so we
> may want to have something even more restrictive since otherwise any
> BPF program could potentially have the same power as the LSM?
>
> - Ted