Messages in this thread | | | Date | Wed, 23 Feb 2022 17:53:07 -0800 | From | Eric Biggers <> | Subject | Re: [PATCH] crypto: drbg: fix crypto api abuse |
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On Wed, Feb 23, 2022 at 05:47:25PM -0800, Eric Biggers wrote: > On Wed, Feb 23, 2022 at 10:04:00AM +0200, Gilad Ben-Yossef wrote: > > the drbg code was binding the same buffer to two different > > scatter gather lists and submitting those as source and > > destination to a crypto api operation, thus potentially > > causing HW crypto drivers to perform overlapping DMA > > mappings which are not aware it is the same buffer. > > > > This can have serious consequences of data corruption of > > internal DRBG buffers and wrong RNG output. > > > > Fix this by reusing the same scatter gatther list for both > > src and dst. > > > > Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com> > > Reported-by: Corentin Labbe <clabbe.montjoie@gmail.com> > > Tested-by: Corentin Labbe <clabbe.montjoie@gmail.com> > > Tested-on: r8a7795-salvator-x > > Tested-on: xilinx-zc706 > > Fixes: 43490e8046b5d ("crypto: drbg - in-place cipher operation for CTR") > > Cc: stable@vger.kernel.org > > Where is it documented and tested that the API doesn't allow this? > I wasn't aware of this case; it sounds perfectly allowed to me. > There might be a lot of other users who do this, not just drbg.c. >
Just quickly looking through the code I maintain, there is another place that uses scatterlists like this: in fscrypt_crypt_block() in fs/crypto/crypto.c, the source and destination can be the same. That's just the code I maintain; I'm sure if you looked through the whole kernel you'd find a lot more.
This sounds more like a driver bug, and a case we need to add self-tests for.
- Eric
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