Re: [PATCH - RESEND] crypto: AF_ALG - remove SGL terminator indicator when chaining

On Thu, Sep 21, 2017 at 10:16:53AM +0200, Stephan Mueller wrote:

The SGL is MAX_SGL_ENTS + 1 in size. The last SG entry is used for the
chaining and is properly updated with the sg_chain invocation. During
the filling-in of the initial SG entries, sg_mark_end is called for each
SG entry. This is appropriate as long as no additional SGL is chained
with the current SGL. However, when a new SGL is chained and the last
SG entry is updated with sg_chain, the last but one entry still contains
the end marker from the sg_mark_end. This end marker must be removed as
otherwise a walk of the chained SGLs will cause a NULL pointer
dereference at the last but one SG entry, because sg_next will return
NULL.

The patch only applies to all kernels up to and including 4.13. The
patch 2d97591ef43d0587be22ad1b0d758d6df4999a0b added to 4.14-rc1
introduced a complete new code base which addresses this bug in
a different way. Yet, that patch is too invasive for stable kernels
and was therefore not marked for stable.

Fixes: 8ff590903d5fc ("crypto: algif_skcipher - User-space interface
for skcipher operations")
CC: <redacted>
CC: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Stephan Mueller <redacted>

Acked-by: Herbert Xu <herbert@gondor.apana.org.au>

Thanks,
-- 
Email: Herbert Xu [off-list ref]
Home Page: http://gondor.apana.org.au/~herbert/
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