hpre: optimize key process before free

driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

In this patch, we try to optimize key process before free of hpre
module.
1、for DH algorithm, we use para g to compute public key, para g is
public, so we need not clear it before free.
2、for RSA algorithm, we should use memzero_explicit to clear prikey.
It will be optimized, when memset follows free.
3、For standard RSA algorithm, we use one buf to store public and
prikey, to consider performance, we just clear prikey buf.
Signed-off-by: NYu'an Wang <wangyuan46@huawei.com>
Reviewed-by: NCheng Hu <hucheng.hu@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/crypto/hisilicon/hpre/hpre_crypto.c

@@ -559,7 +559,6 @@ static void hpre_dh_clear_ctx(struct hpre_ctx *ctx, bool is_clear_all)
 		hisi_qm_stop_qp(ctx->qp);
 
 	if (ctx->dh.g) {
-		memzero_explicit(ctx->dh.g, sz);
 		dma_free_coherent(dev, sz, ctx->dh.g, ctx->dh.dma_g);
 		ctx->dh.g = NULL;
 	}
@@ -893,7 +892,7 @@ static int hpre_rsa_setkey_crt(struct hpre_ctx *ctx, struct rsa_key *rsa_key)
 
 free_key:
 	offset = hlf_ksz * HPRE_CRT_PRMS;
-	memset(ctx->rsa.crt_prikey, 0, offset);
+	memzero_explicit(ctx->rsa.crt_prikey, offset);
 	dma_free_coherent(dev, hlf_ksz * HPRE_CRT_PRMS, ctx->rsa.crt_prikey,
 			  ctx->rsa.dma_crt_prikey);
 	ctx->rsa.crt_prikey = NULL;
@@ -926,7 +925,7 @@ static void hpre_rsa_clear_ctx(struct hpre_ctx *ctx, bool is_clear_all)
 	}
 
 	if (ctx->rsa.prikey) {
-		memzero_explicit(ctx->rsa.prikey, ctx->key_sz << 1);
+		memzero_explicit(ctx->rsa.prikey, ctx->key_sz);
 		dma_free_coherent(dev, ctx->key_sz << 1, ctx->rsa.prikey,
 				  ctx->rsa.dma_prikey);
 		ctx->rsa.prikey = NULL;