linux-kernel - RE: [PATCH v2 00/39] Shadowstacks for userspace

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Message-ID: <752d296b68f04c2282bd898cf7ec3f0f@AcuMS.aculab.com>
Date:   Tue, 4 Oct 2022 09:57:48 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Kees Cook' <keescook@...omium.org>, Jann Horn <jannh@...gle.com>
CC:     Rick Edgecombe <rick.p.edgecombe@...el.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
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        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
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        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
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        Florian Weimer <fweimer@...hat.com>,
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        "dethoma@...rosoft.com" <dethoma@...rosoft.com>
Subject: RE: [PATCH v2 00/39] Shadowstacks for userspace

From: Kees Cook <keescook@...omium.org>
...
> >
> > If you don't want /proc/$pid/mem to be able to do stuff like that,
> > then IMO the way to go is to change when /proc/$pid/mem uses
> > FOLL_FORCE, or to limit overall write access to /proc/$pid/mem.
> 
> Yeah, all reasonable. I just wish we could ditch FOLL_FORCE; it continues
> to weird me out how powerful that fd's side-effects are.

Could you remove FOLL_FORCE from /proc/$pid/mem and add a
/proc/$pid/mem_force that enable FOLL_FORCE but requires root
(or similar) access.

Although I suspect gdb may like to have write access to
code?

	David

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