From: Chris von Recklinghausen > Sent: 12 April 2021 20:51 ... > > This is not about BIOS bugs. Hibernation is deep suspend/resume > > grafted onto cold boot, and it is perfectly legal for the firmware to > > present a different memory map to the OS after a cold boot. It is > > Linux that decides that it can restore the entire system state from a > > swap file, and carry on as if the cold boot was just a [firmware > > assisted] suspend/resume. > > > > So forging collisions is *not* a concern here. Let's avoid accidental > > or malicious, as those adjectives seem to confuse some people. The > > bottom line is that there is no need to protect against deliberate > > attempts to hide the fact that the memory map has changed, and so > > there is no reason to use cryptographic hashes here. > > > How about : > > The check is intended to differentiate between a resume (which expects > an identical e820 map to the one saved in suspend), and a cold boot > (which need not have an identical e820 map to that saved in suspend if > any was done at all). It is not necessary here to protect against > deliberate attempts to hide the fact that the memory map has changed, so > crc32 is sufficient for detection. That sort of implies that the 'resume' and 'cold boot' are differenciated. But the previous comment rather implies that it is the presence of a valid saved image that signifies a 'resume'. An interesting failure case would be moving the disk to a different system. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
