This patch to fix the origin "char *data" memory leak, code style issue
and add necessary check here.
Reported-by: Coverity (CID 1402785)

Signed-off-by: Zhang Chen <chen.zhang@intel.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Jason Wang <jasowang@redhat.com>