[PATCH] crypto: sm2 - remove unnecessary reset operations

[Tianjia Zhang]

This is an algorithm optimization. The reset operation when
setting the public key is repeated and redundant, so remove it.
At the same time, `sm2_ecc_os2ec()` is optimized to make the
function more simpler and more in line with the Linux code style.

Signed-off-by: Tianjia Zhang <tianjia.zh...@linux.alibaba.com>
---
 crypto/sm2.c | 75 ++++++++++++++++++++--------------------------------
 1 file changed, 29 insertions(+), 46 deletions(-)

diff --git a/crypto/sm2.c b/crypto/sm2.c
index 767e160333f6..b21addc3ac06 100644
--- a/crypto/sm2.c
+++ b/crypto/sm2.c
@@ -119,12 +119,6 @@ static void sm2_ec_ctx_deinit(struct mpi_ec_ctx *ec)
        memset(ec, 0, sizeof(*ec));
 }
 
-static int sm2_ec_ctx_reset(struct mpi_ec_ctx *ec)
-{
-       sm2_ec_ctx_deinit(ec);
-       return sm2_ec_ctx_init(ec);
-}
-
 /* RESULT must have been initialized and is set on success to the
  * point given by VALUE.
  */
@@ -132,55 +126,48 @@ static int sm2_ecc_os2ec(MPI_POINT result, MPI value)
 {
        int rc;
        size_t n;
-       const unsigned char *buf;
-       unsigned char *buf_memory;
+       unsigned char *buf;
        MPI x, y;
 
-       n = (mpi_get_nbits(value)+7)/8;
-       buf_memory = kmalloc(n, GFP_KERNEL);
-       rc = mpi_print(GCRYMPI_FMT_USG, buf_memory, n, &n, value);
-       if (rc) {
-               kfree(buf_memory);
-               return rc;
-       }
-       buf = buf_memory;
+       n = MPI_NBYTES(value);
+       buf = kmalloc(n, GFP_KERNEL);
+       if (!buf)
+               return -ENOMEM;
 
-       if (n < 1) {
-               kfree(buf_memory);
-               return -EINVAL;
-       }
-       if (*buf != 4) {
-               kfree(buf_memory);
-               return -EINVAL; /* No support for point compression.  */
-       }
-       if (((n-1)%2)) {
-               kfree(buf_memory);
-               return -EINVAL;
-       }
-       n = (n-1)/2;
+       rc = mpi_print(GCRYMPI_FMT_USG, buf, n, &n, value);
+       if (rc)
+               goto err_freebuf;
+
+       rc = -EINVAL;
+       if (n < 1 || ((n - 1) % 2))
+               goto err_freebuf;
+       /* No support for point compression */
+       if (*buf != 0x4)
+               goto err_freebuf;
+
+       rc = -ENOMEM;
+       n = (n - 1) / 2;
        x = mpi_read_raw_data(buf + 1, n);
-       if (!x) {
-               kfree(buf_memory);
-               return -ENOMEM;
-       }
+       if (!x)
+               goto err_freebuf;
        y = mpi_read_raw_data(buf + 1 + n, n);
-       kfree(buf_memory);
-       if (!y) {
-               mpi_free(x);
-               return -ENOMEM;
-       }
+       if (!y)
+               goto err_freex;
 
        mpi_normalize(x);
        mpi_normalize(y);
-
        mpi_set(result->x, x);
        mpi_set(result->y, y);
        mpi_set_ui(result->z, 1);
 
-       mpi_free(x);
-       mpi_free(y);
+       rc = 0;
 
-       return 0;
+       mpi_free(y);
+err_freex:
+       mpi_free(x);
+err_freebuf:
+       kfree(buf);
+       return rc;
 }
 
 struct sm2_signature_ctx {
@@ -399,10 +386,6 @@ static int sm2_set_pub_key(struct crypto_akcipher *tfm,
        MPI a;
        int rc;
 
-       rc = sm2_ec_ctx_reset(ec);
-       if (rc)
-               return rc;
-
        ec->Q = mpi_point_new(0);
        if (!ec->Q)
                return -ENOMEM;
-- 
2.19.1.3.ge56e4f7