Re: [PATCH v17 08/10] PM: hibernate: disable when there are active secretmem users

On Mon 08-02-21 11:53:58, David Hildenbrand wrote: > On 08.02.21 11:51, Michal Hocko wrote: >> On Mon 08-02-21 11:32:11, David Hildenbrand wrote: >>> On 08.02.21 11:18, Michal Hocko wrote: >>>> On Mon 08-02-21 10:49:18, Mike Rapoport wrote: >>>>> From: Mike Rapoport <rppt(a)linux.ibm.com&gt; >>>>> >>>>> It is unsafe to allow saving of secretmem areas to the hibernation >>>>> snapshot as they would be visible after the resume and this essentially >>>>> will defeat the purpose of secret memory mappings. >>>>> >>>>> Prevent hibernation whenever there are active secret memory users. >>>> >>>> Does this feature need any special handling? As it is effectivelly >>>> unevictable memory then it should behave the same as other mlock, ramfs >>>> which should already disable hibernation as those cannot be swapped out, >>>> no? >>>> >>> >>> Why should unevictable memory not go to swap when hibernating? We're merely >>> dumping all of our system RAM (including any unmovable allocations) to swap >>> storage and the system is essentially completely halted. >>> >> My understanding is that mlock is never really made visible via swap >> storage. > > "Using swap storage for hibernation" and "swapping at runtime" are two > different things. I might be wrong, though. Well, mlock is certainly used to keep sensitive information, not only to protect from major/minor faults.