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

[Herbert Xu <herbert@gondor.apana.org.au>]

On Fri, Dec 01, 2017 at 09:11:57AM +0100, Antoine Tenart wrote:
>
> I agree this should not be the case.
> 
> But:
> - 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.
> 
> I'm not entirely sure what was the code path that leads to this, I'll
> reproduce the issue and try to understand what is going on (I clearly
> recall having this crash though).

That's different.  In that case an unconditional copy is made
regardless of whether the operation is final or update.  That's
why a check is required.

If the operation is finup/final/digest then req->result must be
set and you don't need to check it.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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