Fix coverity defects: CID 147443, 147656, 147655, 147441, 147653

coverity scan CID:147443, Type: Buffer not null terminated
coverity scan CID:147656, Type: Copy into fixed size buffer
coverity scan CID:147655, Type: Copy into fixed size buffer
coverity scan CID:147441, Type: Buffer not null terminated
coverity scan CID:147653, Type: Copy into fixed size buffer

Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: liuhuang <liu.huang@zte.com.cn>
Closes #5165