On July 22, 2022 2:12:03 AM Martin KaFai Lau <kafai@xxxxxx> wrote: > On Thu, Jul 21, 2022 at 12:28:04PM -0500, Frederick Lawler wrote: >> 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. -- paul-moore.com
