On Tue, Aug 2, 2022 at 5:25 PM KP Singh [off-list ref] wrote:

On Mon, Aug 1, 2022 at 5:19 PM Paul Moore [off-list ref] wrote:

quoted

On Mon, Aug 1, 2022 at 9:13 AM Frederick Lawler [off-list ref] wrote:

quoted

On 7/22/22 7:20 AM, Paul Moore wrote:

quoted

On July 22, 2022 2:12:03 AM Martin KaFai Lau [off-list ref] wrote:

quoted

On Thu, Jul 21, 2022 at 12:28:04PM -0500, Frederick Lawler wrote:

quoted

While creating a LSM BPF MAC policy to block user namespace creation, we
used the LSM cred_prepare hook because that is the closest hook to prevent
a call to create_user_ns().

The calls look something like this:

cred = prepare_creds()
security_prepare_creds()
call_int_hook(cred_prepare, ...
if (cred)
create_user_ns(cred)

We noticed that error codes were not propagated from this hook and
introduced a patch [1] to propagate those errors.

The discussion notes that security_prepare_creds()
is not appropriate for MAC policies, and instead the hook is
meant for LSM authors to prepare credentials for mutation. [2]

Ultimately, we concluded that a better course of action is to introduce
a new security hook for LSM authors. [3]

This patch set first introduces a new security_create_user_ns() function
and userns_create LSM hook, then marks the hook as sleepable in BPF.

Patch 1 and 4 still need review from the lsm/security side.

This patchset is in my review queue and assuming everything checks out, I expect to merge it after the upcoming merge window closes.

I would also need an ACK from the BPF LSM folks, but they're CC'd on this patchset.

Based on last weeks comments, should I go ahead and put up v4 for
5.20-rc1 when that drops, or do I need to wait for more feedback?

In general it rarely hurts to make another revision, and I think
you've gotten some decent feedback on this draft, especially around
the BPF LSM tests; I think rebasing on Linus tree after the upcoming
io_uring changes are merged would be a good idea.

As I was typing up my reply I realized I mistakenly mentioned the
io_uring changes that Linus just merged today - oops!  If you haven't
figured it out already, you can disregard that comment, that's a
completely different problem and a completely different set of patches
:)

quoted

Although as a
reminder to the BPF LSM folks - I'm looking at you KP Singh :) - I
need an ACK from you guys before I merge the BPF related patches

Apologies, I was on vacation. I am looking at the patches now.
Reviews and acks coming soon :)

No worries, we've still got the two weeks of the merge window before I
can do anything into linux-next - thanks KP!

-- 
paul-moore.com