[I'm just going to trim the incredibly long list of recipients. Too
many bounces, and I doubt any of them really care]
On Wed, Jan 25, 2023 at 11:21:56AM -0800, Suren Baghdasaryan wrote:
> On Wed, Jan 25, 2023 at 10:37 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
> > Here's a trick I saw somewhere in the VFS:
> >
> > union {
> > const vm_flags_t vm_flags;
> > vm_flags_t __private __vm_flags;
> > };
> >
> > Now it can be read by anybody but written only by those using
> > ACCESS_PRIVATE.
>
> Huh, this is quite nice! I think it does not save us from the cases
> when vma->vm_flags is passed by a reference and modified indirectly,
> like in ksm_madvise()? Though maybe such usecases are so rare (I found
> only 2 cases) that we can ignore this?
Taking the address of vma->vm_flags will give you a const-qualified
pointer, which gcc will then warn about passing to a non-const-qualified
function argument, so I think we're good?
