linux-kernel - Re: [PATCH 00/10] Control Flow Enforcement

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Date:   Tue, 26 Jun 2018 07:56:57 -0700
From:   Yu-cheng Yu <yu-cheng.yu@...el.com>
To:     Andy Lutomirski <luto@...nel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Jann Horn <jannh@...gle.com>,
        Florian Weimer <fweimer@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-doc@...r.kernel.org,
        Linux-MM <linux-mm@...ck.org>,
        linux-arch <linux-arch@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. J. Lu" <hjl.tools@...il.com>,
        "Shanbhogue, Vedvyas" <vedvyas.shanbhogue@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Jonathan Corbet <corbet@....net>,
        Oleg Nesterov <oleg@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        mike.kravetz@...cle.com
Subject: Re: [PATCH 00/10] Control Flow Enforcement - Part (3)

On Mon, 2018-06-25 at 22:26 -0700, Andy Lutomirski wrote:
> On Thu, Jun 7, 2018 at 7:41 AM Yu-cheng Yu <yu-cheng.yu@...el.com>
> wrote:
> > 
> > 
> > This series introduces CET - Shadow stack
> I think you should add some mitigation against sigreturn-oriented
> programming.  How about creating some special token on the shadow
> stack that indicates the presence of a signal frame at a particular
> address when delivering a signal and verifying and popping that token
> in sigreturn?  The token could be literally the address of the signal
> frame, and you could make this unambiguous by failing sigreturn if
> CET
> is on and the signal frame is in executable memory.
> 
> IOW, it would be a shame if sigreturn() itself became a convenient
> CET-bypassing gadget.
> 
> --Andy

I will look into that.

Thanks,
Yu-cheng