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

["Joshua Peisach" <jpeisach@ubuntu.com>]

On Thu May 7, 2026 at 3:05 AM EDT, Sasha Levin wrote:
>
> 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 lot of recent kernel issues sit in code paths most installs only have enabled
> to support a relative minority of users: AF_ALG, ksmbd, nf_tables, vsock, ax25,
> and friends.
>
> For most users, the cost of "this socket family stops working for the day" is
> much smaller than the cost of running a known vulnerable kernel until the fix
> land.

I like the concept - but is there any way to ensure that important functions
like malloc aren't being patched? Or some way to make sure that what is being
patched will not kill the entire kernel?

I know this probably boils down to "operator has to use it correctly", but just
wondering if this was considered.

-Josh