Re: [PATCH] crypto: ccp - Fix AES XTS error for request sizes above 4096

[Tom Lendacky <thomas.lendacky@amd.com>]

On 05/20/2016 06:35 PM, Herbert Xu wrote:
> On Fri, May 20, 2016 at 05:33:03PM -0500, Tom Lendacky wrote:
>> The ccp-crypto module for AES XTS support has a bug that can allow requests
>> greater than 4096 bytes in size to be passed to the CCP hardware. The CCP
>> hardware does not support request sizes larger than 4096, resulting in
>> incorrect output. The request should actually be handled by the fallback
>> mechanism instantiated by the ccp-crypto module.
>>
>> Add a check to insure the request size is less than or equal to the maximum
>> supported size and use the fallback mechanism if it is not.
>>
>> Cc: <stable@vger.kernel.org> # 3.14.x-
>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> 
> I'm OK with this patch but I think it doesn't always need to go into
> the fallback.  I made a test vector split as 4064 bytes + 48 bytes
> and ccp handled it just fine.  It appears that the bug is actually
> in the handling of a single SG entry that's longer than a page,
> presumably because sg_next is used unconditionally instead of
> checking whether there is more in the current SG entry.

I'll take a closer look at this. Something obviously isn't right but
the code doesn't do anything related to PAGE size checks and works
on the length specified in the SG entry.

> 
> But I'll merge your fix as it fixes a real problem.

Thanks Herbert.

Tom

> 
> Thanks,
>