[PATCH] crypto: vmx - fix copy-paste error in CTR mode

[Daniel Axtens]

Hi Eric,

>> The original assembly imported from OpenSSL has two copy-paste
>> errors in handling CTR mode. When dealing with a 2 or 3 block tail,
>> the code branches to the CBC decryption exit path, rather than to
>> the CTR exit path.
>
> So does this need to be fixed in OpenSSL too?

Yes, I'm getting in touch with some people internally (at IBM) about
doing that.

>> This leads to corruption of the IV, which leads to subsequent blocks
>> being corrupted.
>> 
>> This can be detected with libkcapi test suite, which is available at
>> https://github.com/smuellerDD/libkcapi
>> 
>
> Is this also detected by the kernel's crypto self-tests, and if not why not?
> What about with the new option CONFIG_CRYPTO_MANAGER_EXTRA_TESTS=y?

It seems the self-tests do not catch it. To catch it, there has to be a
test where the blkcipher_walk creates a walk.nbytes such that
[(the number of AES blocks) mod 8] is either 2 or 3. This happens with
AF_ALG pretty frequently, but when I booted with self-tests it only hit
1, 4, 5, 6 and 7 - it missed 0, 2 and 3.

I don't have the EXTRA_TESTS option - I'm testing with 5.0-rc6. Is it in
-next?

Regards,
Daniel

>> Reported-by: Ondrej Mosnáček <omosnacek at gmail.com>
>> Fixes: 5c380d623ed3 ("crypto: vmx - Add support for VMS instructions by ASM")
>> Cc: stable at vger.kernel.org
>> Signed-off-by: Daniel Axtens <dja at axtens.net>
>> ---
>>  drivers/crypto/vmx/aesp8-ppc.pl | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/crypto/vmx/aesp8-ppc.pl b/drivers/crypto/vmx/aesp8-ppc.pl
>> index d6a9f63d65ba..de78282b8f44 100644
>> --- a/drivers/crypto/vmx/aesp8-ppc.pl
>> +++ b/drivers/crypto/vmx/aesp8-ppc.pl
>> @@ -1854,7 +1854,7 @@ Lctr32_enc8x_three:
>>  	stvx_u		$out1,$x10,$out
>>  	stvx_u		$out2,$x20,$out
>>  	addi		$out,$out,0x30
>> -	b		Lcbc_dec8x_done
>> +	b		Lctr32_enc8x_done
>>  
>>  .align	5
>>  Lctr32_enc8x_two:
>> @@ -1866,7 +1866,7 @@ Lctr32_enc8x_two:
>>  	stvx_u		$out0,$x00,$out
>>  	stvx_u		$out1,$x10,$out
>>  	addi		$out,$out,0x20
>> -	b		Lcbc_dec8x_done
>> +	b		Lctr32_enc8x_done
>>  
>>  .align	5
>>  Lctr32_enc8x_one:
>> -- 
>> 2.19.1
>>