cifs: Use kmemdup in SMB2_ioctl_init()

Use kmemdup rather than duplicating its implementation

This was reported by coccinelle.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/smb2pdu.c

@@ -2550,12 +2550,11 @@ SMB2_ioctl_init(struct cifs_tcon *tcon, struct smb_rqst *rqst,
 		 * indatalen is usually small at a couple of bytes max, so
 		 * just allocate through generic pool
 		 */
-		in_data_buf = kmalloc(indatalen, GFP_NOFS);
+		in_data_buf = kmemdup(in_data, indatalen, GFP_NOFS);
 		if (!in_data_buf) {
 			cifs_small_buf_release(req);
 			return -ENOMEM;
 		}
-		memcpy(in_data_buf, in_data, indatalen);
 	}
 
 	req->CtlCode = cpu_to_le32(opcode);