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

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: <CABi2SkXLdL37LxLuo+W=rUOrBKfMbxgkkR+s3TqnnS-eAQbakg@mail.gmail.com>
Date: Mon, 24 Feb 2025 11:42:31 -0800
From: Jeff Xu <jeffxu@...omium.org>
To: Kees Cook <kees@...nel.org>
Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>, 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, linux-hardening@...r.kernel.org, 
	linux-mm@...ck.org, jorgelo@...omium.org, sroettger@...gle.com, hch@....de, 
	ojeda@...nel.org, thomas.weissschuh@...utronix.de, adobriyan@...il.com, 
	johannes@...solutions.net, pedro.falcato@...il.com, hca@...ux.ibm.com, 
	willy@...radead.org, anna-maria@...utronix.de, mark.rutland@....com, 
	linus.walleij@...aro.org, Jason@...c4.com, deller@....de, 
	rdunlap@...radead.org, davem@...emloft.net, peterx@...hat.com, 
	f.fainelli@...il.com, gerg@...nel.org, dave.hansen@...ux.intel.com, 
	mingo@...nel.org, ardb@...nel.org, mhocko@...e.com, 42.hyeyoo@...il.com, 
	peterz@...radead.org, ardb@...gle.com, enh@...gle.com, rientjes@...gle.com, 
	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 11:25 AM Kees Cook <kees@...nel.org> wrote:
>
> On Mon, Feb 24, 2025 at 11:10:22AM -0800, Jeff Xu wrote:
> > On Mon, Feb 24, 2025 at 11:03 AM Liam R. Howlett
> > <Liam.Howlett@...cle.com> wrote:
> > >
> > > * Jeff Xu <jeffxu@...omium.org> [250224 13:44]:
> > > > On Mon, Feb 24, 2025 at 10:21 AM Dave Hansen <dave.hansen@...el.com> wrote:
> > > > >
> > > > > On 2/24/25 09:45, jeffxu@...omium.org wrote:
> > > > > > +/*
> > > > > > + * mseal of userspace process's system mappings.
> > > > > > + */
> > > > > > +#ifdef CONFIG_MSEAL_SYSTEM_MAPPINGS
> > > > > > +#define MSEAL_SYSTEM_MAPPINGS_VM_FLAG        VM_SEALED
> > > > > > +#else
> > > > > > +#define MSEAL_SYSTEM_MAPPINGS_VM_FLAG        VM_NONE
> > > > > > +#endif
> > > > >
> > > > > This ends up looking pretty wonky in practice:
> > > > >
> > > > > > +     vm_flags = VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|VM_PFNMAP;
> > > > > > +     vm_flags |= MSEAL_SYSTEM_MAPPINGS_VM_FLAG;
> > > > >
> > > > > because MSEAL_SYSTEM_MAPPINGS_VM_FLAG is so much different from the
> > > > > other ones.
> > > > >
> > > > > Would it really hurt to have
> > > > >
> > > > >  #ifdef CONFIG_64BIT
> > > > >  /* VM is sealed, in vm_flags */
> > > > >  #define VM_SEALED       _BITUL(63)
> > > > > +#else
> > > > > +#define VM_SEALED       VM_NONE
> > > > >  #endif
> > > > >
> > > > > ?
> > > > >
> > > > VM_SEALED isn't defined in 32-bit systems, and mseal.c isn't part of
> > > > the build. This is intentional. Any 32-bit code trying to use the
> > > > sealing function or the VM_SEALED flag will immediately fail
> > > > compilation. This makes it easier to identify incorrect usage.
> > > >
> > >
> > > The reason that two #defines are needed is because you can have mseal
> > > enabled while not sealing system mappings, so for this to be clean we
> > > need two defines.
> > >
> > > However MSEAL_SYSTEM_MAPPINGS_VM_FLAG, is _way_ too long, in my opinion.
> > > Keeping with "VM_SEALED" I'd suggest "VM_SYSTEM_SEALED".
> > >
> > How about MSEAL_SYSTME_MAPPINGS as Kees suggested ?
> >
> > The VM_SYSTEM_SEALED doesn't have the MSEAL key or the MAPPING, so it
> > might take longer for the new reader to understand what it is.
>
> I think to address Dave's concern, it should start with "VM_". We use
> "SEAL" already with VM_SEALED, so the "M" in "MSEAL" may be redundant,
> and to clarify the system mapping, how avout VM_SEAL_SYSMAP  ? That
> capture's, hopefully, Dave, Liam, and your thoughts about the naming?
>
Liam had a comment in the previous version, asking everything related
with mseal() to have the MSEAL keyword, that is why KCONFIG change has
MSEAL.

How about VM_MSEAL_SYSMAP ?

-Jeff

> --
> Kees Cook