Re: [PATCH v26 2/5] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs

[Michał Mirosław]

On Thu, 3 Aug 2023 at 17:09, Andrei Vagin <avagin@xxxxxxxxx> wrote:
> On Thu, Jul 27, 2023 at 02:36:34PM +0500, Muhammad Usama Anjum wrote:
[...]
> > +     n_pages = (*end - addr) / PAGE_SIZE;
> > +     if (check_add_overflow(p->found_pages, n_pages, &total_pages) ||
> > +         total_pages > p->arg.max_pages) {
>
> why do we need to use check_add_overflow here?
>
> > +             size_t n_too_much = total_pages - p->arg.max_pages;
>
> it is unsafe to use total_pages if check_add_overflow returns non-zero.

Since we're adding unsigned integers, this is well defined even after overflow.

Best Regards
Michał Mirosław