Re: Locking for HW crypto accelerators

Am Donnerstag, 30. August 2018, 15:09:05 CEST schrieb Krzysztof Kozlowski:

Hi Krzysztof,

Thanks Stephan for hints. Let's assume the each of init, update and
final are atomic... but how about the relation between update and
final? I have two concurrent users in user-space but only one HW:

Process A:             Process B:
init() and set_key()
                       init() and different key
update(some_data)
                       update(different_data)
final()
                       final()

The final() from process A will now produce the result of hashing/CRC
of some_data and different_data (and even maybe mixed with init() for
different key). All because in the meantime process B added its own
data to the HW.

The question is where is the state of the cipher operation kept that is 
produced with each of the init/update/final calls. Your answer implies that 
this state is kept in hardware.

But commonly the state is kept in software. Look at ahash_request for example, 
the __ctx pointer is intended to point to the memory the driver needs to store 
its state.

Pick a random driver implementation and search for ahash_request_ctx, for 
example.

Best regards,
Krzysztof

Ciao
Stephan