linux-kernel - Re: [PATCH 00/35] Shadow stacks for userspace

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Message-ID: <YgI37n+3JfLSNQCQ@grain>
Date:   Tue, 8 Feb 2022 12:29:18 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Adrian Reber <adrian@...as.de>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>, 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-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H . J . Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V . Shankar" <ravi.v.shankar@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        joao.moreira@...el.com, John Allen <john.allen@....com>,
        kcc@...gle.com, eranian@...gle.com,
        Andrei Vagin <avagin@...il.com>,
        Dmitry Safonov <0x7f454c46@...il.com>
Subject: Re: [PATCH 00/35] Shadow stacks for userspace

On Tue, Feb 08, 2022 at 11:16:51AM +0200, Mike Rapoport wrote:
>  
> > Any thoughts on how you would _like_ to see this resolved?
> 
> Ideally, CRIU will need a knob that will tell the kernel/CET machinery
> where the next RET will jump, along the lines of
> restore_signal_shadow_stack() AFAIU.
> 
> But such a knob will immediately reduce the security value of the entire
> thing, and I don't have good ideas how to deal with it :(

Probably a kind of latch in the task_struct which would trigger off once
returt to a different address happened, thus we would be able to jump inside
paratite code. Of course such trigger should be available under proper
capability only.