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    Subject[PATCH 4.4 10/73] crypto: arm/aes-ctr - fix NULL dereference in tail processing
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Ard Biesheuvel <ard.biesheuvel@linaro.org>

    commit f82e90b28654804ab72881d577d87c3d5c65e2bc upstream.

    The AES-CTR glue code avoids calling into the blkcipher API for the
    tail portion of the walk, by comparing the remainder of walk.nbytes
    modulo AES_BLOCK_SIZE with the residual nbytes, and jumping straight
    into the tail processing block if they are equal. This tail processing
    block checks whether nbytes != 0, and does nothing otherwise.

    However, in case of an allocation failure in the blkcipher layer, we
    may enter this code with walk.nbytes == 0, while nbytes > 0. In this
    case, we should not dereference the source and destination pointers,
    since they may be NULL. So instead of checking for nbytes != 0, check
    for (walk.nbytes % AES_BLOCK_SIZE) != 0, which implies the former in
    non-error conditions.

    Fixes: 86464859cc77 ("crypto: arm - AES in ECB/CBC/CTR/XTS modes using ARMv8 Crypto Extensions")
    Reported-by: xiakaixu <xiakaixu@huawei.com>
    Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/arm/crypto/aes-ce-glue.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/arch/arm/crypto/aes-ce-glue.c
    +++ b/arch/arm/crypto/aes-ce-glue.c
    @@ -279,7 +279,7 @@ static int ctr_encrypt(struct blkcipher_
    err = blkcipher_walk_done(desc, &walk,
    walk.nbytes % AES_BLOCK_SIZE);
    }
    - if (nbytes) {
    + if (walk.nbytes % AES_BLOCK_SIZE) {
    u8 *tdst = walk.dst.virt.addr + blocks * AES_BLOCK_SIZE;
    u8 *tsrc = walk.src.virt.addr + blocks * AES_BLOCK_SIZE;
    u8 __aligned(8) tail[AES_BLOCK_SIZE];

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