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

[Serge E. Hallyn]

On Tue, Sep 15, 2026 at 07:44:23PM +0200, Jann Horn wrote:
> 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.

Ah, I'm sorry.  Didn't mean to dispute a prior decision.

Sounds good.

IIUC it's already in a tree, but for the record

Reviewed-by: Serge Hallyn <sergeh at kernel.org>

thanks,
-serge