linux-kernel - Re: [PATCH v1 10/36] mm: sanity-check maximum folio size in folio_set

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ad3ff8d5-a9ea-4f83-9860-a96cc1e728c7@lucifer.local>
Date: Fri, 29 Aug 2025 13:18:05 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, Zi Yan <ziy@...dia.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Brendan Jackman <jackmanb@...gle.com>,
        Christoph Lameter <cl@...two.org>, Dennis Zhou <dennis@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>, dri-devel@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, iommu@...ts.linux.dev,
        io-uring@...r.kernel.org, Jason Gunthorpe <jgg@...dia.com>,
        Jens Axboe <axboe@...nel.dk>, Johannes Weiner <hannes@...xchg.org>,
        John Hubbard <jhubbard@...dia.com>, kasan-dev@...glegroups.com,
        kvm@...r.kernel.org, "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-arm-kernel@...s.com, linux-arm-kernel@...ts.infradead.org,
        linux-crypto@...r.kernel.org, linux-ide@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-mmc@...r.kernel.org, linux-mm@...ck.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-scsi@...r.kernel.org, Marco Elver <elver@...gle.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Michal Hocko <mhocko@...e.com>, Mike Rapoport <rppt@...nel.org>,
        Muchun Song <muchun.song@...ux.dev>, netdev@...r.kernel.org,
        Oscar Salvador <osalvador@...e.de>, Peter Xu <peterx@...hat.com>,
        Robin Murphy <robin.murphy@....com>,
        Suren Baghdasaryan <surenb@...gle.com>, Tejun Heo <tj@...nel.org>,
        virtualization@...ts.linux.dev, Vlastimil Babka <vbabka@...e.cz>,
        wireguard@...ts.zx2c4.com, x86@...nel.org
Subject: Re: [PATCH v1 10/36] mm: sanity-check maximum folio size in
 folio_set_order()

On Fri, Aug 29, 2025 at 12:10:30PM +0200, David Hildenbrand wrote:
> On 28.08.25 17:00, Lorenzo Stoakes wrote:
> > On Thu, Aug 28, 2025 at 12:01:14AM +0200, David Hildenbrand wrote:
> > > Let's sanity-check in folio_set_order() whether we would be trying to
> > > create a folio with an order that would make it exceed MAX_FOLIO_ORDER.
> > >
> > > This will enable the check whenever a folio/compound page is initialized
> > > through prepare_compound_head() / prepare_compound_page().
> >
> > NIT: with CONFIG_DEBUG_VM set :)
>
> Yes, will add that.

Thanks!

>
> >
> > >
> > > Reviewed-by: Zi Yan <ziy@...dia.com>
> > > Signed-off-by: David Hildenbrand <david@...hat.com>
> >
> > LGTM (apart from nit below), so:
> >
> > Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> >
> > > ---
> > >   mm/internal.h | 1 +
> > >   1 file changed, 1 insertion(+)
> > >
> > > diff --git a/mm/internal.h b/mm/internal.h
> > > index 45da9ff5694f6..9b0129531d004 100644
> > > --- a/mm/internal.h
> > > +++ b/mm/internal.h
> > > @@ -755,6 +755,7 @@ static inline void folio_set_order(struct folio *folio, unsigned int order)
> > >   {
> > >   	if (WARN_ON_ONCE(!order || !folio_test_large(folio)))
> > >   		return;
> > > +	VM_WARN_ON_ONCE(order > MAX_FOLIO_ORDER);
> >
> > Given we have 'full-fat' WARN_ON*()'s above, maybe worth making this one too?
>
> The idea is that if you reach this point here, previous such checks I added
> failed. So this is the safety net, and for that VM_WARN_ON_ONCE() is
> sufficient.
>
> I think we should rather convert the WARN_ON_ONCE to VM_WARN_ON_ONCE() at
> some point, because no sane code should ever trigger that.

Ack, ok. I don't think vital for this series though!

>
> --
> Cheers
>
> David / dhildenb
>

Cheers, Lorenzo