Re: [PATCH 23/27] bpf: Restrict kernel image access functions when the kernel is locked down

[Matthew Garrett]

On Wed, Mar 27, 2019 at 8:15 PM James Morris <jmorris@xxxxxxxxx> wrote:
> OTOH, this seems like a combination of mechanism and policy. The 3 modes
> are a help here, but I wonder if they may be too coarse grained still,
> e.g. if someone wants to allow a specific mechanism according to their own
> threat model and mitigations.

In general the interfaces blocked by these patches could also be
blocked with an LSM, and I'd guess that people with more fine-grained
requirements would probably take that approach.

> Secure boot gives you some assurance of the static state of the system at
> boot time, and lockdown is certainly useful (with or without secure boot),
> but it's not a complete solution to runtime kernel integrity protection by
> any stretch of the imagination.  I'm concerned about it being perceived as
> such.

What do you think the functionality gaps are in terms of ensuring
kernel integrity (other than kernel flaws that allow the restrictions
to be bypassed)?