Message-ID: <Y9Fh9joU3vTCwYbX@dhcp22.suse.cz>
Date:   Wed, 25 Jan 2023 18:08:06 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
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Subject: Re: [PATCH v2 4/6] mm: replace vma->vm_flags indirect modification
 in ksm_madvise

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@...roid.com> 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

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