From: Jason Gunthorpe <jgg@ziepe.ca>
To: "David Hildenbrand (Arm)" <david@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Muchun Song <muchun.song@linux.dev>,
Oscar Salvador <osalvador@suse.de>,
Jeff Layton <jlayton@kernel.org>, Chuck Lever <cel@kernel.org>,
Alexander Aring <alex.aring@gmail.com>,
Shuah Khan <shuah@kernel.org>, Gerd Hoffmann <kraxel@redhat.com>,
Vivek Kasireddy <vivek.kasireddy@intel.com>,
Jeff Xu <jeffxu@google.com>, David Matlack <dmatlack@google.com>,
Pasha Tatashin <tatashin@google.com>,
linux-mm@kvack.org, linux-api@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/2] mm/memfd: add F_SEAL_PUNCH_HOLE
Date: Fri, 30 Oct 2026 12:11:15 -0300 [thread overview]
Message-ID: <20261030151115.GD3889730@ziepe.ca> (raw)
In-Reply-To: <2c7aa5c1-3af3-4654-b244-1257d05c9d45@kernel.org>
On Fri, Oct 30, 2026 at 03:39:40PM +0100, David Hildenbrand (Arm) wrote:
> >> I don't see a reason to make userspace (that should not shoot itself into the
> >> foot) a kernel feature it must activate itself to not shoot itself into the foot.
> >
> > The issue is live update doesn't preserve those background punched
> > folios and now we have created an UAF attack on the kernel across
> > kexec if you don't do something about it.
> >
> > There was some notion here that with the right sealing flags we could
> > tell if everything was 'live update compatible' and then know that
> > these attacks are impossible.
> Just remember that there was any hole punch and refuse to live update this instance.
>
> We could likely implement "we saw hole punch on a pinned folio" as well, but I
> don't think that's required initially.
>
> No need for more shaky seals.
Ah, yeah that might work out. It has to be checked really late though,
after userspace cannot change the memfd any further.
Jason
prev parent reply other threads:[~2026-10-30 15:11 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-26 22:05 [PATCH 0/2] mm/memfd: add F_SEAL_PUNCH_HOLE Samiullah Khawaja
2026-10-26 22:05 ` [PATCH 1/2] " Samiullah Khawaja
2026-10-26 22:05 ` [PATCH 2/2] selftests/memfd: add F_SEAL_PUNCH_HOLE tests Samiullah Khawaja
2026-10-26 22:46 ` [PATCH 0/2] mm/memfd: add F_SEAL_PUNCH_HOLE Andy Lutomirski
2026-10-27 22:55 ` Samiullah Khawaja
2026-10-28 3:57 ` Andy Lutomirski
2026-10-29 23:16 ` Samiullah Khawaja
2026-10-30 0:26 ` Andy Lutomirski
2026-10-30 2:11 ` Andy Lutomirski
2026-10-30 12:12 ` Jason Gunthorpe
2026-10-30 14:54 ` Andy Lutomirski
2026-10-30 10:20 ` David Hildenbrand (Arm)
2026-10-30 12:11 ` Jason Gunthorpe
2026-10-30 14:39 ` David Hildenbrand (Arm)
2026-10-30 15:11 ` Jason Gunthorpe [this message]
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