Messages in this thread | | | Date | Mon, 27 Jun 2022 16:18:32 -0700 | Subject | Re: [PATCH 0/2] Introduce security_create_user_ns() | From | Casey Schaufler <> |
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On 6/27/2022 3:27 PM, Paul Moore wrote: > On Mon, Jun 27, 2022 at 6:15 PM Daniel Borkmann <daniel@iogearbox.net> wrote: >> On 6/27/22 11:56 PM, Paul Moore wrote: >>> On Mon, Jun 27, 2022 at 8:11 AM Christian Brauner <brauner@kernel.org> wrote: >>>> On Thu, Jun 23, 2022 at 11:21:37PM -0400, Paul Moore wrote: >>> ... >>> >>>>> This is one of the reasons why I usually like to see at least one LSM >>>>> implementation to go along with every new/modified hook. The >>>>> implementation forces you to think about what information is necessary >>>>> to perform a basic access control decision; sometimes it isn't always >>>>> obvious until you have to write the access control :) >>>> I spoke to Frederick at length during LSS and as I've been given to >>>> understand there's a eBPF program that would immediately use this new >>>> hook. Now I don't want to get into the whole "Is the eBPF LSM hook >>>> infrastructure an LSM" but I think we can let this count as a legitimate >>>> first user of this hook/code. >>> Yes, for the most part I don't really worry about the "is a BPF LSM a >>> LSM?" question, it's generally not important for most discussions. >>> However, there is an issue unique to the BPF LSMs which I think is >>> relevant here: there is no hook implementation code living under >>> security/. While I talked about a hook implementation being helpful >>> to verify the hook prototype, it is also helpful in providing an >>> in-tree example for other LSMs; unfortunately we don't get that same >>> example value when the initial hook implementation is a BPF LSM. >> I would argue that such a patch series must come together with a BPF >> selftest which then i) contains an in-tree usage example, ii) adds BPF >> CI test coverage. Shipping with a BPF selftest at least would be the >> usual expectation. > I'm not going to disagree with that, I generally require matching > tests for new SELinux kernel code, but I was careful to mention code > under 'security/' and not necessarily just a test implementation :) I > don't want to get into a big discussion about it, but I think having a > working implementation somewhere under 'security/' is more > discoverable for most LSM folks.
I agree. It would be unfortunate if we added a hook explicitly for eBPF only to discover that the proposed user needs something different. The LSM community should have a chance to review the code before committing to all the maintenance required in supporting it.
Is there a reference on how to write an eBPF security module? There should be something out there warning the eBPF programmer of the implications of providing a secid_to_secctx hook for starters.
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