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

David Hildenbrand david at redhat.com
Mon Feb 8 06:13:49 EST 2021

On 08.02.21 11:57, Michal Hocko wrote:
> 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 at linux.ibm.com>
>>>>>> 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.

I think you're right in theory, the man page mentions "Cryptographic 
security software often handles critical bytes like passwords or secret 
keys as data structures" ...

however, I am not aware of any such swap handling and wasn't able to 
spot it quickly. Let me take a closer look.


David / dhildenb

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