Killswitch: Per-function short-circuit mitigation primitive
7 hours ago
- #security-mitigation
- #linux-kernel
- #kernel-feature
- Introduces a killswitch feature allowing administrators to short-circuit kernel functions by making them return a fixed value without executing their body, as a temporary security mitigation.
- Implemented via kprobes; engagement is configured through securityfs at /sys/kernel/security/killswitch/. Supported commands include 'engage <symbol> <retval>', 'disengage <symbol>', and 'disengage_all'.
- Adds a new taint flag TAINT_KILLSWITCH (bit 20, character 'H') to indicate when a killswitch is engaged, persisting until reboot.
- Includes boot-time configuration via kernel parameter killswitch=fn1=<val>,fn2=<val>,... for fleet-wide deployment.
- Provides test cases, documentation, and integration with selftests to validate functionality.