Re: [PATCH v2] killswitch: add per-function short-circuit mitigation primitive

[Florian Weimer]

* Sasha Levin:

> When a kernel (security) issue goes public, fleets stay exposed until a patched
> kernel is built, distributed, and rebooted into.
>
> For many such issues the simplest mitigation is to stop calling the buggy
> function. Killswitch provides that. An admin writes:
>
>     echo "engage af_alg_sendmsg -1" \
>         > /sys/kernel/security/killswitch/control
>
> After this, af_alg_sendmsg() returns -EPERM on every call without
> running its body. The mitigation takes effect immediately, and is dropped on
> the next reboot -- by which point a patched kernel is hopefully in place.

Do you expect this to be safe to enable in kernel lockdown mode (i.e.,
with typical Secure Boot configurations in distributions)?