linux-kernel - Re: [RFC PATCH v6 00/26] Control-flow Enforcement: Shadow Stack

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Date:   Mon, 26 Nov 2018 10:29:40 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     Andrew Lutomirski <luto@...nel.org>,
        Florian Weimer <fweimer@...hat.com>,
        "Carlos O'Donell" <carlos@...hat.com>,
        Rich Felker <dalias@...c.org>, X86 ML <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Balbir Singh <bsingharora@...il.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...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>,
        "Shanbhogue, Vedvyas" <vedvyas.shanbhogue@...el.com>
Subject: Re: [RFC PATCH v6 00/26] Control-flow Enforcement: Shadow Stack

On Mon, Nov 26, 2018 at 9:44 AM Yu-cheng Yu <yu-cheng.yu@...el.com> wrote:
>
> On Thu, 2018-11-22 at 08:53 -0800, Andy Lutomirski wrote:
> > [cc some more libc folks]

>
> >
> > 2. I want to be able to modify the signal context from a signal
> > handler such that, when the signal handler returns, it will return to
> > a frame higher up on the call stack than where the signal started and
> > to a different RIP value.  How can I do this?  I guess I can modify
> > the shadow stack with WRSS if WR_SHSTK_EN=1, but how do I tell the
> > kernel to kindly skip the frames I want to skip when I do sigreturn()?
> >
> > The reason I'm asking #2 is that I think it's time to resurrect my old
> > vDSO syscall cancellation helper series here:
> >
> > https://lwn.net/Articles/679434/
>
> If tools/testing/selftests/x86/unwind_vdso.c passes, can we say the kernel does
> the right thing?  Or do you have other tests that I can run?

I haven't written the relevant test yet.  Hopefully soon :)