From: Ma Wupeng <mawupeng1@xxxxxxxxxx>
While testing mlock, we have a problem if the len of mlock is ULONG_MAX.
The return value of mlock is zero. But nothing will be locked since the
len in do_mlock overflows to zero due to the following code in mlock:
len = PAGE_ALIGN(len + (offset_in_page(start)));
However this problem appear in multiple syscalls.
Since TASK_SIZE is the maximum user space address. The start or len of
mlock shouldn't be bigger than this. Function access_ok can be used to
check this issue, so return -EINVAL if bigger.