linux-kernel - Re: [PATCH v6 17/20] mm/mmap: Use vms accounted pages in mmap

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Message-ID: <njy7dm425n3tjbv7zy4i66gnewz6gkxd3ou42jgk73zfn23i4k@yn7apymvp2hn>
Date: Wed, 21 Aug 2024 13:15:56 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Paul Moore <paul@...l-moore.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Suren Baghdasaryan <surenb@...gle.com>,
        Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
        Matthew Wilcox <willy@...radead.org>, Vlastimil Babka <vbabka@...e.cz>,
        sidhartha.kumar@...cle.com, Bert Karwatzki <spasswolf@....de>,
        Jiri Olsa <olsajiri@...il.com>, Kees Cook <kees@...nel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        linux-security-module@...r.kernel.org
Subject: Re: [PATCH v6 17/20] mm/mmap: Use vms accounted pages in
 mmap_region()

* Paul Moore <paul@...l-moore.com> [240821 12:35]:
> On Tue, Aug 20, 2024 at 8:02 PM Liam R. Howlett <Liam.Howlett@...cle.com> wrote:
> >
> > From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> >
> > Change from nr_pages variable to vms.nr_accounted for the charged pages
> > calculation.  This is necessary for a future patch.
> >
> > This also avoids checking security_vm_enough_memory_mm() if the amount
> > of memory won't change.
> >
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> > Cc: Kees Cook <kees@...nel.org>
> > Cc: linux-security-module@...r.kernel.org
> > Reviewed-by: Kees Cook <kees@...nel.org>
> > Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> > Reviewed-by: Suren Baghdasaryan <surenb@...gle.com>
> > ---
> >  mm/mmap.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> I'm pretty sure I already ACK'd this, but I don't see it above so here
> it is again:
> 
> Acked-by: Paul Moore <paul@...l-moore.com> (LSM)

Sorry for missing that.  It's here now for sure.

Thanks,
Liam

> 
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index 19dac138f913..2a4f1df96f94 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -1413,9 +1413,10 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
> >          */
> >         if (accountable_mapping(file, vm_flags)) {
> >                 charged = pglen;
> > -               charged -= nr_accounted;
> > -               if (security_vm_enough_memory_mm(mm, charged))
> > +               charged -= vms.nr_accounted;
> > +               if (charged && security_vm_enough_memory_mm(mm, charged))
> >                         goto abort_munmap;
> > +
> >                 vms.nr_accounted = 0;
> >                 vm_flags |= VM_ACCOUNT;
> >         }
> > --
> > 2.43.0
> 
> -- 
> paul-moore.com