diff --git a/tools/testing/selftests/resctrl/fill_buf.c b/tools/testing/selftests/resctrl/fill_buf.c
index 0f6cca61ec94..6d1d5eed595c 100644
--- a/tools/testing/selftests/resctrl/fill_buf.c
+++ b/tools/testing/selftests/resctrl/fill_buf.c
@@ -135,24 +135,34 @@ static int fill_cache_write(unsigned char *buf, size_t buf_size, bool once)
 	return 0;
 }
 
-static int fill_cache(size_t buf_size, int memflush, int op, bool once)
+static unsigned char *alloc_buffer(size_t buf_size, int memflush)
 {
 	unsigned char *buf;
-	int ret;
 
 	buf = malloc_and_init_memory(buf_size);
 	if (!buf)
-		return -1;
+		return NULL;
 
 	/* Flush the memory before using to avoid "cache hot pages" effect */
 	if (memflush)
 		mem_flush(buf, buf_size);
 
+	return buf;
+}
+
+static int fill_cache(size_t buf_size, int memflush, int op, bool once)
+{
+	unsigned char *buf;
+	int ret;
+
+	buf = alloc_buffer(buf_size, memflush);
+	if (!buf)
+		return -1;
+
 	if (op == 0)
 		ret = fill_cache_read(buf, buf_size, once);
 	else
 		ret = fill_cache_write(buf, buf_size, once);
-
 	free(buf);
 
 	if (ret) {
@@ -160,8 +170,7 @@ static int fill_cache(size_t buf_size, int memflush, int op, bool once)
 		return -1;
 	}
 
-
-	return 0;
+	return ret;
 }
 
 int run_fill_buf(size_t span, int memflush, int op, bool once)