From: Pedro Falcato <pedro.falcato@gmail.com>
To: "Stephen Röttger" <sroettger@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Jeff Xu <jeffxu@google.com>,
jeffxu@chromium.org, akpm@linux-foundation.org,
keescook@chromium.org, jannh@google.com, willy@infradead.org,
gregkh@linuxfoundation.org, jorgelo@chromium.org,
groeck@chromium.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org, linux-mm@kvack.org,
dave.hansen@intel.com, linux-hardening@vger.kernel.org,
deraadt@openbsd.org
Subject: Re: [RFC PATCH v3 11/11] mseal:add documentation
Date: Thu, 14 Dec 2023 20:11:32 +0000 [thread overview]
Message-ID: <CAKbZUD09VKfxsz4VCp+0-Y-cWJ-n=dV+t45Aan10HEhFCjxWdQ@mail.gmail.com> (raw)
In-Reply-To: <CAEAAPHZpYXHNPdca+xfj77bwYaL6PY-c_oQ54r+=wtJa6_hmCA@mail.gmail.com>
On Thu, Dec 14, 2023 at 6:07 PM Stephen Röttger <sroettger@google.com> wrote:
>
> On Thu, Dec 14, 2023 at 2:31 AM Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >
> > On Wed, 13 Dec 2023 at 16:36, Jeff Xu <jeffxu@google.com> wrote:
> > >
> > >
> > > > IOW, when would you *ever* say "seal this area, but MADV_DONTNEED is ok"?
> > > >
> > > The MADV_DONTNEED is OK for file-backed mapping.
> >
> > Right. It makes no semantic difference. So there's no point to it.
> >
> > My point was that you added this magic flag for "not ok for RO anon mapping".
> >
> > It's such a *completely* random flag, that I go "that's just crazy
> > random - make sealing _always_ disallow that case".
> >
> > So what I object to in this series is basically random small details
> > that should just eb part of the basic act of sealing.
> >
> > I think sealing should just mean "you can't do any operations that
> > have semantic meaning for the mapping, because it is SEALED".
> >
> > So I think sealing should automatically mean "can't do MADV_DONTNEED
> > on anon memory", because that's basically equivalent to a munmap/remap
> > operation.
>
> In Chrome, we have a use case to allow MADV_DONTNEED on sealed memory.
I don't want to be that guy (*believe me*), but what if there was a
way to attach BPF programs to mm's? Such that you could handle 'seal
failures' in BPF, and thus allow for this sort of weird semantics?
e.g: madvise(MADV_DONTNEED) on a sealed region fails, kernel invokes
the BPF program (that chrome loaded), BPF program sees it was a
MADV_DONTNEED and allows it to proceed.
It requires BPF but sounds like a good compromise in order to not get
an ugly API?
--
Pedro
next prev parent reply other threads:[~2023-12-14 20:11 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-12 23:16 [RFC PATCH v3 00/11] Introduce mseal() jeffxu
2023-12-12 23:16 ` [RFC PATCH v3 01/11] mseal: Add mseal syscall jeffxu
2023-12-13 7:24 ` Greg KH
2023-12-12 23:16 ` [RFC PATCH v3 02/11] mseal: Wire up " jeffxu
2023-12-12 23:16 ` [RFC PATCH v3 03/11] mseal: add can_modify_mm and can_modify_vma jeffxu
2023-12-12 23:16 ` [RFC PATCH v3 04/11] mseal: add MM_SEAL_BASE jeffxu
2023-12-12 23:16 ` [RFC PATCH v3 05/11] mseal: add MM_SEAL_PROT_PKEY jeffxu
2023-12-12 23:17 ` [RFC PATCH v3 06/11] mseal: add sealing support for mmap jeffxu
2023-12-12 23:17 ` [RFC PATCH v3 07/11] mseal: make sealed VMA mergeable jeffxu
2023-12-12 23:17 ` [RFC PATCH v3 08/11] mseal: add MM_SEAL_DISCARD_RO_ANON jeffxu
2023-12-12 23:17 ` [RFC PATCH v3 09/11] mseal: add MAP_SEALABLE to mmap() jeffxu
2023-12-12 23:17 ` [RFC PATCH v3 10/11] selftest mm/mseal memory sealing jeffxu
2023-12-31 6:39 ` Muhammad Usama Anjum
2023-12-12 23:17 ` [RFC PATCH v3 11/11] mseal:add documentation jeffxu
2023-12-13 0:39 ` Linus Torvalds
2023-12-14 0:35 ` Jeff Xu
2023-12-14 1:09 ` Theo de Raadt
2023-12-14 1:31 ` Linus Torvalds
2023-12-14 18:06 ` Stephen Röttger
2023-12-14 20:11 ` Pedro Falcato [this message]
2023-12-14 20:14 ` Linus Torvalds
2023-12-14 22:52 ` Jeff Xu
2024-01-20 15:23 ` Theo de Raadt
2024-01-20 16:40 ` Linus Torvalds
2024-01-20 16:59 ` Theo de Raadt
2024-01-21 0:16 ` Jeff Xu
2024-01-21 0:43 ` Theo de Raadt
2023-12-14 15:04 ` Theo de Raadt
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