[$] Locking down hibernation for the winter

When a computer hibernates, the kernel writes the contents of memory to disk andthen shuts the system down. Resuming from hibernation involves reading that databack into memory, and then having the kernel pick up where it left off.Unfortunately, the kernel does not haveany way to know that the data it is reading back has not been tampered with,which is why lockdown, an optional kernelfeature that attempts to prevent modifications to the running kernel, disables hibernation.Matthew Garrett, who has been working on lockdown for many years, has shareda patch set that aims to fix this problem. His solution must also protectagainst downgrade attacks (where an attacker reboots the computer with an olderkernel version to bypass new protections), which complicates the implementation.