Re: [PATCH bpf-next v7 4/8] bpf: lsm: Implement attach, detach and execution

[Stephen Smalley]

On 3/26/20 8:24 PM, James Morris wrote:
> On Thu, 26 Mar 2020, KP Singh wrote:
>
> > +int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
> > +			const struct bpf_prog *prog)
> > +{
> > +	/* Only CAP_MAC_ADMIN users are allowed to make changes to LSM hooks
> > +	 */
> > +	if (!capable(CAP_MAC_ADMIN))
> > +		return -EPERM;
> > +
>
> Stephen, can you confirm that your concerns around this are resolved
> (IIRC, by SELinux implementing a bpf_prog callback) ?

I guess the only residual concern I have is that CAP_MAC_ADMIN means 
something different to SELinux (ability to get/set file security 
contexts unknown to the currently loaded policy), so leaving the 
CAP_MAC_ADMIN check here (versus calling a new security hook here and 
checking CAP_MAC_ADMIN in the implementation of that hook for the 
modules that want that) conflates two very different things.  Prior to 
this patch, there are no users of CAP_MAC_ADMIN outside of individual 
security modules; it is only checked in module-specific logic within 
apparmor, safesetid, selinux, and smack, so the meaning was module-specific.