Re: [PATCH v2 0/2] Introduce the pkill_on_warn parameter

From: Kees Cook
Date: Thu Nov 18 2021 - 12:32:08 EST

On Tue, Nov 16, 2021 at 11:00:23AM -0800, Casey Schaufler wrote:
> On 11/16/2021 10:41 AM, Kees Cook wrote:
> > On Tue, Nov 16, 2021 at 12:12:16PM +0300, Alexander Popov wrote:
> > > What if the Linux kernel had a LSM module responsible for error handling policy?
> > > That would require adding LSM hooks to BUG*(), WARN*(), KERN_EMERG, etc.
> > > In such LSM policy we can decide immediately how to react on the kernel error.
> > > We can even decide depending on the subsystem and things like that.
> > That would solve the "atomicity" issue the WARN tracepoint solution has,
> > and it would allow for very flexible userspace policy.
> >
> > I actually wonder if the existing panic_on_* sites should serve as a
> > guide for where to put the hooks. The current sysctls could be replaced
> > by the hooks and a simple LSM.
> Do you really want to make error handling a "security" issue?
> If you add security_bug(), security_warn_on() and the like
> you're begging that they be included in SELinux (AppArmor) policy.
> BPF, too, come to think of it. Is that what you want?

Yeah, that is what I was thinking. This would give the LSM a view into
kernel state, which seems a reasonable thing to do. If system integrity
is compromised, an LSM may want to stop trusting things.

A dedicated error-handling LSM could be added for those hooks that
implemented the existing default panic_on_* sysctls, and could expand on
that logic for other actions.

Kees Cook