On Mon, 5 Dec 2022 11:41:05 +0800 Wupeng Ma <mawupeng1@xxxxxxxxxx> wrote: > 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))); > > The same problem happens in munlock. > > 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. What happens if userspace uses a value somewhat smaller than ULONG_MAX? mlock(addr, ULONG_MAX - 1000000); ? Because if the above works successfully and if it no longer works successfully with this patchset then that could be a backward-compatibility problem.
