linux-kernel - Re: [PATCH v6 1/7] mseal, system mappings: kernel config and header change

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Message-ID: <CABi2SkU_-4sZgM8cTaEev_1V=M0QHk3=DK3ZBFr4Le7-d_v+7A@mail.gmail.com>
Date: Mon, 24 Feb 2025 11:33:44 -0800
From: Jeff Xu <jeffxu@...omium.org>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>, Jeff Xu <jeffxu@...omium.org>, 
	Kees Cook <kees@...nel.org>, Dave Hansen <dave.hansen@...el.com>, akpm@...ux-foundation.org, 
	jannh@...gle.com, torvalds@...ux-foundation.org, vbabka@...e.cz, 
	lorenzo.stoakes@...cle.com, adhemerval.zanella@...aro.org, oleg@...hat.com, 
	avagin@...il.com, benjamin@...solutions.net, linux-kernel@...r.kernel.org, 
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	groeck@...omium.org, mpe@...erman.id.au, aleksandr.mikhalitsyn@...onical.com, 
	mike.rapoport@...il.com
Subject: Re: [PATCH v6 1/7] mseal, system mappings: kernel config and header change

On Mon, Feb 24, 2025 at 11:32 AM Liam R. Howlett
<Liam.Howlett@...cle.com> wrote:
>
> * Jeff Xu <jeffxu@...omium.org> [250224 14:23]:
> > On Mon, Feb 24, 2025 at 11:11 AM Liam R. Howlett
> > <Liam.Howlett@...cle.com> wrote:
> > >
> > > * Kees Cook <kees@...nel.org> [250224 13:55]:
> > > > On Mon, Feb 24, 2025 at 10:52:13AM -0800, Dave Hansen wrote:
> > > > > On 2/24/25 10:44, Jeff Xu wrote:
> > > > > > For example:
> > > > > > Consider the case below in src/third_party/kernel/v6.6/fs/proc/task_mmu.c,
> > > > > >
> > > > > > #ifdef CONFIG_64BIT
> > > > > > [ilog2(VM_SEALED)] = "sl",
> > > > > > #endif
> > > > > >
> > > > > > Redefining VM_SEALED  to VM_NONE for 32 bit won't detect the problem
> > > > > > in case that  "#ifdef CONFIG_64BIT" line is missing.
> > > > > >
> > > > > > Please note, this has been like this since the first version of
> > > > > > mseal() RFC patch, and I prefer to keep it this way.
> > > > >
> > > > > That logic is reasonable. But it's different from the _vast_ majority of
> > > > > other flags.
> > > > >
> > > > > So what justifies VM_SEALED being so different? It's leading to pretty
> > > > > objectively ugly code in this series.
> > > >
> > > > Note that VM_SEALED is the "is this VMA sealed?" bit itself. The define
> > > > for "should we perform system mapping sealing?" is intentionally separate
> > > > here, so that it can be Kconfig and per-arch toggled, etc.
> > > >
> > >
> > > Considering Dave is the second person that did not find the huge commit
> > > message helpful, can we please limit the commit message to be about the
> > > actual code and not the entire series?
> > >
> > > I thought we said that it was worth while making this change in v5?
> > >
> > I include the cover letter's content in the first commit message to
> > clearly communicate the purpose of the entire patch series, saving
> > maintainers' time when accepting the patch.
>
> Having more text than patch for such a patch seems unreasonable.  I'd
> find it more acceptable if it were a complicated race condition, but
> everyone is getting lost in the summary.
>
I will remove the cover letter from the first patch then.

> >
> > Should I still include that, and add what the first patch does, and
> > separate it from the cover letter with  "----"? What do you think?
>
> Here is my v5 answer, I think it was clear about not putting the entire
> summary into the first patch.
>
Thanks.

> [1]. https://lore.kernel.org/all/ml3x5qchmnehdzz2rxsdcdghivaqffojiweuhvpvzw45u3l5bh@23sblrom3m36/
>
> Thanks,
> Liam