[PATCH 2/5] crypto: virtio - Simplify RSA key size caching

[Lukas Wunner]

When setting a public or private RSA key, the integer n is cached in the
transform context virtio_crypto_akcipher_ctx -- with the sole purpose of
calculating the key size from it in virtio_crypto_rsa_max_size().
It looks like this was copy-pasted from crypto/rsa.c.

Cache the key size directly instead of the integer n, thus simplifying
the code and reducing the memory footprint.

Signed-off-by: Lukas Wunner <lu...@wunner.de>
---
 .../virtio/virtio_crypto_akcipher_algs.c      | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c 
b/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c
index 48fee07b7e51..7fdf32c79909 100644
--- a/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c
+++ b/drivers/crypto/virtio/virtio_crypto_akcipher_algs.c
@@ -21,7 +21,7 @@
 #include "virtio_crypto_common.h"
 
 struct virtio_crypto_rsa_ctx {
-       MPI n;
+       unsigned int key_size;
 };
 
 struct virtio_crypto_akcipher_ctx {
@@ -352,10 +352,7 @@ static int virtio_crypto_rsa_set_key(struct 
crypto_akcipher *tfm,
        int node = virtio_crypto_get_current_node();
        uint32_t keytype;
        int ret;
-
-       /* mpi_free will test n, just free it. */
-       mpi_free(rsa_ctx->n);
-       rsa_ctx->n = NULL;
+       MPI n;
 
        if (private) {
                keytype = VIRTIO_CRYPTO_AKCIPHER_KEY_TYPE_PRIVATE;
@@ -368,10 +365,13 @@ static int virtio_crypto_rsa_set_key(struct 
crypto_akcipher *tfm,
        if (ret)
                return ret;
 
-       rsa_ctx->n = mpi_read_raw_data(rsa_key.n, rsa_key.n_sz);
-       if (!rsa_ctx->n)
+       n = mpi_read_raw_data(rsa_key.n, rsa_key.n_sz);
+       if (!n)
                return -ENOMEM;
 
+       rsa_ctx->key_size = mpi_get_size(n);
+       mpi_free(n);
+
        if (!ctx->vcrypto) {
                vcrypto = virtcrypto_get_dev_node(node, 
VIRTIO_CRYPTO_SERVICE_AKCIPHER,
                                                VIRTIO_CRYPTO_AKCIPHER_RSA);
@@ -442,7 +442,7 @@ static unsigned int virtio_crypto_rsa_max_size(struct 
crypto_akcipher *tfm)
        struct virtio_crypto_akcipher_ctx *ctx = akcipher_tfm_ctx(tfm);
        struct virtio_crypto_rsa_ctx *rsa_ctx = &ctx->rsa_ctx;
 
-       return mpi_get_size(rsa_ctx->n);
+       return rsa_ctx->key_size;
 }
 
 static int virtio_crypto_rsa_init_tfm(struct crypto_akcipher *tfm)
@@ -460,12 +460,9 @@ static int virtio_crypto_rsa_init_tfm(struct 
crypto_akcipher *tfm)
 static void virtio_crypto_rsa_exit_tfm(struct crypto_akcipher *tfm)
 {
        struct virtio_crypto_akcipher_ctx *ctx = akcipher_tfm_ctx(tfm);
-       struct virtio_crypto_rsa_ctx *rsa_ctx = &ctx->rsa_ctx;
 
        virtio_crypto_alg_akcipher_close_session(ctx);
        virtcrypto_dev_put(ctx->vcrypto);
-       mpi_free(rsa_ctx->n);
-       rsa_ctx->n = NULL;
 }
 
 static struct virtio_crypto_akcipher_algo virtio_crypto_akcipher_algs[] = {
-- 
2.43.0