_do_sha256_sum(): Fix missing error check.

Coverity scan has correctly spotted that Sha256Init() and related
functions may return an error.

Honestly I don't know /how/ any of these can return an error, since the
context is the only part that should allocate, but it's defined that
way.

Signed-off-by: Peter Jones <pjones@redhat.com>

Author: vathpela

pe.c

@@ -50,9 +50,14 @@ _do_sha256_sum(void *addr, UINTN size, UINT8 *digest)
 	if (sha256ctx == NULL)
 		return EFI_OUT_OF_RESOURCES;
 
-	Sha256Init(sha256ctx);
-	Sha256Update(sha256ctx, addr, size);
-	Sha256Final(sha256ctx, digest);
+	if (!Sha256Init(sha256ctx))
+		return EFI_OUT_OF_RESOURCES;
+
+	if (!Sha256Update(sha256ctx, addr, size))
+		return EFI_OUT_OF_RESOURCES;
+
+	if (!Sha256Final(sha256ctx, digest))
+		return EFI_OUT_OF_RESOURCES;
 
 	FreePool(sha256ctx);
 	return EFI_SUCCESS;