[PATCH v3 2/3] proc: query LSMs for introspective mem access (if PROC_MEM_FORCE_ALWAYS)

[Jann Horn]

On Tue, Sep 15, 2026 at 7:04 PM Serge Hallyn (AMD) <sergeh at kernel.org> wrote:
> On Mon, Sep 07, 2026 at 11:00:17PM +0200, Jann Horn wrote:
> > +/**
> > + * security_mem_foll_force() - Check if FOLL_FORCE is allowed
> > + * @subject: credentials using which /proc/$pid/mem was opened
> > + * @opened_by_owner: whether checks on open() were bypassed because the opener
> > + *                   has the same MM as the target
> > + *
> > + * Check if FOLL_FORCE is allowed for accessing process memory through
> > + * /proc/$pid/mem. opened_by_owner signals whether the opener's MM was the same
> > + * as the target MM, meaning the security_ptrace_access_check() hook was
> > + * bypassed on open().
> > + * (Current current->mm does not matter for this; for example, if write() is
> > + * called on an FD that was received from another process which obtained it with
> > + * open("/proc/self/mem"), @opened_by_owner is still true.)
> > + *
> > + * Note that this hook is only designed to be useful in the opened_by_owner
> > + * case, where the subject credentials effectively also describe the object.
>
> Given this, would it make more sense to call the hook something
> like `security_mem_foll_force_self()` and only call it in the
> opened_by_owner==true case?
>
> I only suggest it because it seems to lower the cognitive load
> when looking at this code, so it might make it easier to maintain.

I agree with you, and that is what I did in the previous versions. :P

But given that two relevant maintainers disagreed with me, I changed
it in this version.