On 2023/1/2 21:22, David Hildenbrand wrote: > On 05.12.22 04:41, Wupeng Ma wrote: >> 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. > > I assume this makes sure that what we document holds: > > EINVAL (mlock(), mlock2(), and munlock()) The result of the addition > addr+len was less than addr (e.g., the addition may have > resulted in an overflow). > > So instead of adding access_ok() checks, wouldn't be the right think to do checking for overflows? I agree with you. Do checking only for overflows do seems nice since we need to keep backward-compatibility. > >
