Re: [PATCH v2 8/8] crypto/testmgr: Allocate only the required output size for hash tests

2017-01-12 Thread Herbert Xu 
On Tue, Jan 10, 2017 at 03:24:46PM -0800, Andy Lutomirski wrote:
> There are some hashes (e.g. sha224) that have some internal trickery
> to make sure that only the correct number of output bytes are
> generated.  If something goes wrong, they could potentially overrun
> the output buffer.
> 
> Make the test more robust by allocating only enough space for the
> correct output size so that memory debugging will catch the error if
> the output is overrun.
> 
> Tested by intentionally breaking sha224 to output all 256
> internally-generated bits while running on KASAN.
> 
> Cc: Ard Biesheuvel 
> Cc: Herbert Xu 
> Signed-off-by: Andy Lutomirski 

Patch applied.  Thanks.
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Re: [PATCH v2 8/8] crypto/testmgr: Allocate only the required output size for hash tests

2017-01-11 Thread Andy Lutomirski 
On Wed, Jan 11, 2017 at 11:47 PM, Herbert Xu
 wrote:
> Andy Lutomirski  wrote:
>> There are some hashes (e.g. sha224) that have some internal trickery
>> to make sure that only the correct number of output bytes are
>> generated.  If something goes wrong, they could potentially overrun
>> the output buffer.
>>
>> Make the test more robust by allocating only enough space for the
>> correct output size so that memory debugging will catch the error if
>> the output is overrun.
>>
>> Tested by intentionally breaking sha224 to output all 256
>> internally-generated bits while running on KASAN.
>>
>> Cc: Ard Biesheuvel 
>> Cc: Herbert Xu 
>> Signed-off-by: Andy Lutomirski 
>
> This patch doesn't seem to depend on anything else in the series.
> Do you want me to take it separately?

Yes, please.  Its only relation to the rest of the series is that I
wanted to make sure that I didn't mess up sha224's finalization code.

--Andy
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Re: [PATCH v2 8/8] crypto/testmgr: Allocate only the required output size for hash tests

2017-01-11 Thread Herbert Xu 
Andy Lutomirski  wrote:
> There are some hashes (e.g. sha224) that have some internal trickery
> to make sure that only the correct number of output bytes are
> generated.  If something goes wrong, they could potentially overrun
> the output buffer.
> 
> Make the test more robust by allocating only enough space for the
> correct output size so that memory debugging will catch the error if
> the output is overrun.
> 
> Tested by intentionally breaking sha224 to output all 256
> internally-generated bits while running on KASAN.
> 
> Cc: Ard Biesheuvel 
> Cc: Herbert Xu 
> Signed-off-by: Andy Lutomirski 

This patch doesn't seem to depend on anything else in the series.
Do you want me to take it separately?

Cheers,
-- 
Email: Herbert Xu 
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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Re: [PATCH v2 8/8] crypto/testmgr: Allocate only the required output size for hash tests

2017-01-11 Thread Andy Lutomirski 
On Wed, Jan 11, 2017 at 7:13 AM, David Laight  wrote:
> From: Andy Lutomirski
>> Sent: 10 January 2017 23:25
>> There are some hashes (e.g. sha224) that have some internal trickery
>> to make sure that only the correct number of output bytes are
>> generated.  If something goes wrong, they could potentially overrun
>> the output buffer.
>>
>> Make the test more robust by allocating only enough space for the
>> correct output size so that memory debugging will catch the error if
>> the output is overrun.
>
> Might be better to test this by allocating an overlong buffer
> and then explicitly checking that the output hasn't overrun
> the allowed space.
>
> If nothing else the error message will be clearer.

I thought about that, but then I'd have to figure out what poison
value to use.  Both KASAN and the usual slab debugging are quite good
at this kind of checking, and KASAN will even point you to the
problematic code directly.

--Andy


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Andy Lutomirski
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RE: [PATCH v2 8/8] crypto/testmgr: Allocate only the required output size for hash tests

2017-01-11 Thread David Laight 
From: Andy Lutomirski
> Sent: 10 January 2017 23:25
> There are some hashes (e.g. sha224) that have some internal trickery
> to make sure that only the correct number of output bytes are
> generated.  If something goes wrong, they could potentially overrun
> the output buffer.
> 
> Make the test more robust by allocating only enough space for the
> correct output size so that memory debugging will catch the error if
> the output is overrun.

Might be better to test this by allocating an overlong buffer
and then explicitly checking that the output hasn't overrun
the allowed space.

If nothing else the error message will be clearer.

David

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