Re: [PATCH 2/4] crypto: drbg wait for crypto op not signal safe

Re: [PATCH 2/4] crypto: drbg wait for crypto op not signal safe

[Eric Biggers]

Hi Gilad,

On Thu, May 11, 2017 at 02:53:43PM +0300, Gilad Ben-Yossef wrote:
> drbg_kcapi_sym_ctr() was using wait_for_completion_interruptible() to
> wait for completion of async crypto op but if a signal occurs it
> may return before DMA ops of HW crypto provider finish, thus
> corrupting the output buffer.
> 
> Resolve this by using wait_for_completion() instead.
> 
> Reported-by: Eric Biggers <ebiggers3@gmail.com>
> Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
> CC: stable@vger.kernel.org
> ---
>  crypto/drbg.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/crypto/drbg.c b/crypto/drbg.c
> index fa749f4..fa9054d 100644
> --- a/crypto/drbg.c
> +++ b/crypto/drbg.c
> @@ -1767,8 +1767,7 @@ static int drbg_kcapi_sym_ctr(struct drbg_state *drbg,
>  			break;
>  		case -EINPROGRESS:
>  		case -EBUSY:
> -			ret = wait_for_completion_interruptible(
> -				&drbg->ctr_completion);
> +			ret = wait_for_completion(&drbg->ctr_completion);
>  			if (!ret && !drbg->ctr_async_err) {
>  				reinit_completion(&drbg->ctr_completion);
>  				break;
> -- 

wait_for_completion() doesn't return a value.  This was fixed in the next patch,
but it should be done in this patch.

Eric

Re: [PATCH 4/4] crypto: Documentation: fix none signal safe sample

[Eric Biggers]

On Thu, May 11, 2017 at 02:53:45PM +0300, Gilad Ben-Yossef wrote:
> The sample code was showing use of wait_for_completion_interruptible()
> for waiting for an async. crypto op to finish. However, if a signal
> arrived it would free the buffers used even while crypto HW might
> still DMA from/into the buffers.
> 
> Resolve this by using wait_for_completion() instead.
> 
> Reported-by: Eric Biggers <ebiggers3@gmail.com>
> Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
> ---
>  Documentation/crypto/api-samples.rst | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Documentation/crypto/api-samples.rst b/Documentation/crypto/api-samples.rst
> index d021fd9..944f08b 100644
> --- a/Documentation/crypto/api-samples.rst
> +++ b/Documentation/crypto/api-samples.rst
> @@ -48,7 +48,7 @@ Code Example For Symmetric Key Cipher Operation
>              break;
>          case -EINPROGRESS:
>          case -EBUSY:
> -            rc = wait_for_completion_interruptible(
> +            rc = wait_for_completion(
>                  &sk->result.completion);
>              if (!rc && !sk->result.err) {
>                  reinit_completion(&sk->result.completion);
> -- 
> 2.1.4
> 

Same issue here: wait_for_completion() doesn't return a value.

Eric

Re: [PATCH 2/4] crypto: drbg wait for crypto op not signal safe

[Herbert Xu]

On Thu, May 11, 2017 at 02:53:43PM +0300, Gilad Ben-Yossef wrote:
> drbg_kcapi_sym_ctr() was using wait_for_completion_interruptible() to
> wait for completion of async crypto op but if a signal occurs it
> may return before DMA ops of HW crypto provider finish, thus
> corrupting the output buffer.
> 
> Resolve this by using wait_for_completion() instead.
> 
> Reported-by: Eric Biggers <ebiggers3@gmail.com>
> Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
> CC: stable@vger.kernel.org

This patch doesn't even compile.  Please test your work first.

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH 2/4] crypto: drbg wait for crypto op not signal safe

[Gilad Ben-Yossef]

On Thu, May 18, 2017 at 8:09 AM, Herbert Xu <herbert@gondor.apana.org.au> wrote:
> On Thu, May 11, 2017 at 02:53:43PM +0300, Gilad Ben-Yossef wrote:
>> drbg_kcapi_sym_ctr() was using wait_for_completion_interruptible() to
>> wait for completion of async crypto op but if a signal occurs it
>> may return before DMA ops of HW crypto provider finish, thus
>> corrupting the output buffer.
>>
>> Resolve this by using wait_for_completion() instead.
>>
>> Reported-by: Eric Biggers <ebiggers3@gmail.com>
>> Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
>> CC: stable@vger.kernel.org
>
> This patch doesn't even compile.  Please test your work first.

Sigh... I've noticed it, fixed it, compiled it and than went ahead and
squashed the fix with the next patch in series instead of this one
like an idiot.

Please accept my apologies for wasting your time. I'll send a fixed version.

Gilad

>
> Thanks,
> --
> Email: Herbert Xu <herbert@gondor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt



-- 
Gilad Ben-Yossef
Chief Coffee Drinker

"If you take a class in large-scale robotics, can you end up in a
situation where the homework eats your dog?"
 -- Jean-Baptiste Queru