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

[Sasha Levin <sashal@kernel.org>]

On Thu, May 07, 2026 at 09:21:15AM -0600, Jonathan Corbet wrote:
>Sasha Levin <sashal@kernel.org> writes:
>
>> When a (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.
>
>A quick look suggests that you're not checking lockdown status.  I don't
>doubt for a second that this thing could be used to bypass lockdown - by
>shorting out security_locked_down() if nothing else.  I'm guessing that
>might not prove entirely popular.

Hmm... Good point. I'll respin a v2 adressing this and Greg's comments.

-- 
Thanks,
Sasha