There is a copy-paste error where sha256_mb_mgr_get_comp_job_avx2()
copies the SHA-256 digest state from sha256_mb_mgr::args::digest to
job_sha256::result_digest.  Consequently, the sha256_mb algorithm
sometimes calculates the wrong digest.  Fix it.

Reproducer using AF_ALG:

    #include <assert.h>
    #include <linux/if_alg.h>
    #include <stdio.h>
    #include <string.h>
    #include <sys/socket.h>
    #include <unistd.h>

    static const __u8 expected[32] =
        "\xad\x7f\xac\xb2\x58\x6f\xc6\xe9\x66\xc0\x04\xd7\xd1\xd1\x6b\x02"
        "\x4f\x58\x05\xff\x7c\xb4\x7c\x7a\x85\xda\xbd\x8b\x48\x89\x2c\xa7";

    int main()
    {
        int fd;
        struct sockaddr_alg addr = {
            .salg_type = "hash",
            .salg_name = "sha256_mb",
        };
        __u8 data[4096] = { 0 };
        __u8 digest[32];
        int ret;
        int i;

        fd = socket(AF_ALG, SOCK_SEQPACKET, 0);
        bind(fd, (void *)&addr, sizeof(addr));
        fork();
        fd = accept(fd, 0, 0);
        do {
            ret = write(fd, data, 4096);
            assert(ret == 4096);
            ret = read(fd, digest, 32);
            assert(ret == 32);
        } while (memcmp(digest, expected, 32) == 0);

        printf("wrong digest: ");
        for (i = 0; i < 32; i++)
            printf("%02x", digest[i]);
        printf("\n");
    }

Output was:

    wrong digest: ad7facb2000000000000000000000000ffffffef7cb47c7a85dabd8b48892ca7

Fixes: 172b1d6b ("crypto: sha256-mb - fix ctx pointer and digest copy")
Cc: <stable@vger.kernel.org> # v4.8+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>