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

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Message-ID: <CALCETrXK6hypCb5sXwxWRKr=J6_7XtS6s5GB1WPBiqi79q8-8g@mail.gmail.com>
Date:   Tue, 12 Jun 2018 09:00:03 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     bsingharora@...il.com, 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 Tue, Jun 12, 2018 at 8:06 AM Yu-cheng Yu <yu-cheng.yu@...el.com> wrote:
>
> On Tue, 2018-06-12 at 20:56 +1000, Balbir Singh wrote:
> >
> > On 08/06/18 00:37, Yu-cheng Yu wrote:
> > > This series introduces CET - Shadow stack
> > >
> > > At the high level, shadow stack is:
> > >
> > >     Allocated from a task's address space with vm_flags VM_SHSTK;
> > >     Its PTEs must be read-only and dirty;
> > >     Fixed sized, but the default size can be changed by sys admin.
> > >
> > > For a forked child, the shadow stack is duplicated when the next
> > > shadow stack access takes place.
> > >
> > > For a pthread child, a new shadow stack is allocated.
> > >
> > > The signal handler uses the same shadow stack as the main program.
> > >
> >
> > Even with sigaltstack()?
> >
> >
> > Balbir Singh.
>
> Yes.
>

I think we're going to need some provision to add an alternate signal
stack to handle the case where the shadow stack overflows.