Re: [PATCH v4.19.y, v4.14.y, v4.9.y] crypto: drbg - add FIPS 140-2 CTRNG for noise source

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Feb 27, 2020 at 05:58:05AM +0000, Vikash Bansal wrote:
> From: Stephan Mueller <smueller@chronox.de>
> 
> commit db07cd26ac6a418dc2823187958edcfdb415fa83 upstream
> 
> FIPS 140-2 section 4.9.2 requires a continuous self test of the noise
> source. Up to kernel 4.8 drivers/char/random.c provided this continuous
> self test. Afterwards it was moved to a location that is inconsistent
> with the FIPS 140-2 requirements. The relevant patch was
> e192be9d9a30555aae2ca1dc3aad37cba484cd4a .
> 
> Thus, the FIPS 140-2 CTRNG is added to the DRBG when it obtains the
> seed. This patch resurrects the function drbg_fips_continous_test that
> existed some time ago and applies it to the noise sources. The patch
> that removed the drbg_fips_continous_test was
> b3614763059b82c26bdd02ffcb1c016c1132aad0 .
> 
> The Jitter RNG implements its own FIPS 140-2 self test and thus does not
> need to be subjected to the test in the DRBG.
> 
> The patch contains a tiny fix to ensure proper zeroization in case of an
> error during the Jitter RNG data gathering.
> 
> Signed-off-by: Stephan Mueller <smueller@chronox.de>
> Reviewed-by: Yann Droneaud <ydroneaud@opteya.com>
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> Signed-off-by: Vikash Bansal <bvikas@vmware.com>
> ---
>  crypto/drbg.c         | 94 +++++++++++++++++++++++++++++++++++++++++--
>  include/crypto/drbg.h |  2 +
>  2 files changed, 93 insertions(+), 3 deletions(-)

This looks like a new feature to me, why is it needed in the stable
kernel trees?  What bug does it fix?

thanks,

greg k-h