Re: [PATCH v2 4/6] mm: replace vma->vm_flags indirect modification in ksm_madvise

[Michal Hocko]

On Wed 25-01-23 08:57:48, Suren Baghdasaryan wrote:
> On Wed, Jan 25, 2023 at 1:38 AM 'Michal Hocko' via kernel-team
> <kernel-team@xxxxxxxxxxx> wrote:
> >
> > On Wed 25-01-23 00:38:49, Suren Baghdasaryan wrote:
> > > Replace indirect modifications to vma->vm_flags with calls to modifier
> > > functions to be able to track flag changes and to keep vma locking
> > > correctness. Add a BUG_ON check in ksm_madvise() to catch indirect
> > > vm_flags modification attempts.
> >
> > Those BUG_ONs scream to much IMHO. KSM is an MM internal code so I
> > gueess we should be willing to trust it.
> 
> Yes, but I really want to prevent an indirect misuse since it was not
> easy to find these. If you feel strongly about it I will remove them
> or if you have a better suggestion I'm all for it.

You can avoid that by making flags inaccesible directly, right?

-- 
Michal Hocko
SUSE Labs