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

Jeff Xu
2025-02-24T18:59:32Z

On Mon, Feb 24, 2025 at 10:55 AM Kees Cook <kees@kernel.org> wrote:
>
> 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.
>
Ya, it is a layer of separation also. Thanks for pointing it out.

> As for the name, I have no strong opinion. Perhaps VM_SEALED_SYSTEM_MAPPING ?
>
OK.

Thanks
-Jeff

> -Kees
>
> --
> Kees Cook