Fix memleak in EVP_DigestSignFinal/VerifyFinal.

Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3658)

crypto/evp/m_sigver.c

@@ -123,8 +123,12 @@ int EVP_DigestSignFinal(EVP_MD_CTX *ctx, unsigned char *sigret,
                 r = EVP_DigestFinal_ex(ctx, md, &mdlen);
         } else {
             EVP_MD_CTX *tmp_ctx = EVP_MD_CTX_new();
-            if (tmp_ctx == NULL || !EVP_MD_CTX_copy_ex(tmp_ctx, ctx))
+            if (tmp_ctx == NULL)
                 return 0;
+            if (!EVP_MD_CTX_copy_ex(tmp_ctx, ctx)) {
+                EVP_MD_CTX_free(tmp_ctx);
+                return 0;
+            }
             if (sctx)
                 r = tmp_ctx->pctx->pmeth->signctx(tmp_ctx->pctx,
                                                   sigret, siglen, tmp_ctx);
@@ -178,8 +182,12 @@ int EVP_DigestVerifyFinal(EVP_MD_CTX *ctx, const unsigned char *sig,
             r = EVP_DigestFinal_ex(ctx, md, &mdlen);
     } else {
         EVP_MD_CTX *tmp_ctx = EVP_MD_CTX_new();
-        if (tmp_ctx == NULL || !EVP_MD_CTX_copy_ex(tmp_ctx, ctx))
+        if (tmp_ctx == NULL)
+            return -1;
+        if (!EVP_MD_CTX_copy_ex(tmp_ctx, ctx)) {
+            EVP_MD_CTX_free(tmp_ctx);
             return -1;
+        }
         if (vctx) {
             r = tmp_ctx->pctx->pmeth->verifyctx(tmp_ctx->pctx,
                                                 sig, siglen, tmp_ctx);