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    Subject[PATCH 4.4 27/66] [PATCH - RESEND] crypto: AF_ALG - remove SGL terminator indicator when chaining
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Stephan Mueller <smueller@chronox.de>

    Fixed differently upstream as commit 2d97591ef43d ("crypto: af_alg - consolidation of duplicate code")

    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")
    Signed-off-by: Stephan Mueller <smueller@chronox.de>
    Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    crypto/algif_skcipher.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    --- a/crypto/algif_skcipher.c
    +++ b/crypto/algif_skcipher.c
    @@ -143,8 +143,10 @@ static int skcipher_alloc_sgl(struct soc
    sg_init_table(sgl->sg, MAX_SGL_ENTS + 1);
    sgl->cur = 0;

    - if (sg)
    + if (sg) {
    sg_chain(sg, MAX_SGL_ENTS + 1, sgl->sg);
    + sg_unmark_end(sg + (MAX_SGL_ENTS - 1));
    + }

    list_add_tail(&sgl->list, &ctx->tsgl);
    }

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