Re: [PATCH v3] killswitch: add per-function short-circuit mitigation primitive

On Thu, May 21, 2026 at 7:38 AM Sasha Levin <[email protected]> wrote:
>
> On Tue, May 19, 2026 at 03:00:15PM -0700, Song Liu wrote:
> >On Tue, May 19, 2026 at 12:57 PM Sasha Levin <[email protected]> wrote:
> >[...]
> >> >Fully agree with Song here that there is no clear boundary, and that the
> >> >killswitch could lead to arbitrary, hard to debug breakage if applied to
> >> >the wrong function.. introducing worse bugs than the one being mitigated
> >> >or even /short-circuit LSM enforcement/ (engage security_file_open 0,
> >> >engage cap_capable 0, engage apparmor_* etc).
> >>
> >> This is similar to livepatch, right? Do we need guardrails there too?
> >
> >livepatch has the same guardrails as other kernel modules:
> >CONFIG_MODULE_SIG, CONFIG_MODULE_SIG_FORCE, etc.
>
> Which the user can choose to enable or disable. Livepatches will work just fine
> with CONFIG_MODULE_SIG=n, right?
>
> With the whitelist approach, the user has no choice but to accept it.
>
> Would it make sense to allow disabling the whitelist via a kernel config or
> some runtime flag?

I personally think it makes sense to have options to allow bypassing/blocking
more kernel functions than the current allow list. But I don't know whether
we would like to go all the way to allow it for all the ftrace-able functions.
I think we will need some careful analysis on this.

Thanks,
Song