On Sat, May 09, 2026 at 02:02:24PM +0200, Florian Weimer wrote:
* 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)?
Yes: under lockdown, killswitch has to be configured on the cmdline. Runtime engage is gated on the new LOCKDOWN_KILLSWITCH reason. I do need to resend a v3 that also gates disengage and the retval write so a cmdline-installed mitigation is fixed for the boot - I didn't think about that scenario. -- Thanks, Sasha
