Re: [PATCH v2 3/4] crypto: inside-secure - only update the result buffer when provided

[Antoine Tenart <antoine.tenart@free-electrons.com>]

Hi Kamil,

On Fri, Dec 01, 2017 at 11:18:30AM +0100, Kamil Konieczny wrote:
> On 01.12.2017 09:11, Antoine Tenart wrote:
> > - Other drivers are doing this check (grep "if (!req->result)" or
> >   "if (req->result)" to see some of them).
> > - I see at least one commit fixing the exact same issue I'm facing here,
> >   393897c5156a415533ff85aa381458840417b032:
> > 
> >     crypto: ccp - Check for caller result area before using it
> > 
> >     For a hash operation, the caller doesn't have to supply a result
> >     area on every call so don't use it / update it if it hasn't
> >     been supplied.
> 
> Do you set last_req true for digest/finup/final ? If yes,
> then you need to copy result only when it is true,
> 
> 	if (sreq->last_req) {
> 		result_sz = crypto_ahash_digestsize(ahash);
> 		memcpy(sreq->state, areq->result, result_sz);
> 	}

Yes the last_req flag is set for the last request, so when
digest/finup/final are called. But no we can't copy the result into the
state based on this as an user might want to perform multiple updates,
then export the context, to import it again before sending more updates.

Antoine

-- 
Antoine Ténart, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com