if(copy_from_user(&dltmp, argp, sizeof(struct dl_str)))
                return -EFAULT;
-       if(dltmp.cardno < 0 || dltmp.cardno >= MAX_BOARDS)
+       if(dltmp.cardno < 0 || dltmp.cardno >= MAX_BOARDS || dltmp.len < 0)
                return -EINVAL;
 
        switch(cmd)
        void __iomem *baseAddr;
        int i;
 
+       if(len < 0 || len > sizeof(moxaBuff))
+               return -EINVAL;
        if(copy_from_user(moxaBuff, tmp, len))
                return -EFAULT;
        baseAddr = moxa_boards[cardno].basemem;
        void __iomem *baseAddr;
        int i;
 
-       if(len > sizeof(moxaBuff))
+       if(len < 0 || len > sizeof(moxaBuff))
                return -EINVAL;
        if(copy_from_user(moxaBuff, tmp, len))
                return -EFAULT;
        void __iomem *baseAddr, *ofsAddr;
        int retval, port, i;
 
+       if(len < 0 || len > sizeof(moxaBuff))
+               return -EINVAL;
        if(copy_from_user(moxaBuff, tmp, len))
                return -EFAULT;
        baseAddr = moxa_boards[cardno].basemem;