Patch derived from below Xen changeset.
Signed-off-by: Christopher Clark <christopher.clark6@baesystems.com>

commit 22bf5be3237cb482a2ffd772ffd20ce37285eebf
Author: Olaf Hering <olaf@aepfle.de>
Date:   Mon Jun 18 14:55:36 2018 +0200

stubdom/vtpm: fix memcmp in TPM_ChangeAuthAsymFinish

gcc8 spotted this error:
error: 'memcmp' reading 20 bytes from a region of size 8 [-Werror=stringop-overflow=]

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

diff --git a/tpm/tpm_deprecated.c b/tpm/tpm_deprecated.c
index c362b56..4c49f54 100644
--- a/tpm/tpm_deprecated.c
+++ b/tpm/tpm_deprecated.c
@@ -434,7 +434,7 @@ TPM_RESULT TPM_ChangeAuthAsymFinish(TPM_KEY_HANDLE parentHandle,
   tpm_hmac_final(&hmac_ctx, b1.digest);
   /* 6. The TPM SHALL compare b1 with newAuthLink. The TPM SHALL
         indicate a failure if the values do not match. */
-  if (memcmp(&b1, &newAuthLink, sizeof(TPM_HMAC))) {
+  if (memcmp(&b1, newAuthLink, sizeof(TPM_HMAC))) {
     debug("TPM_ChangeAuthAsymFinish(): newAuthLink value does not match.");
     return TPM_FAIL;
   }