linux-kernel - Re: [RFC PATCH v4 24/27] mm/mmap: Create a guard area between VMAs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20181003163226.GC9449@asgard.redhat.com>
Date:   Wed, 3 Oct 2018 18:32:26 +0200
From:   Eugene Syromiatnikov <esyr@...hat.com>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     Andy Lutomirski <luto@...capital.net>, 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>, 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>,
        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>,
        "Shanbhogue, Vedvyas" <vedvyas.shanbhogue@...el.com>
Subject: Re: [RFC PATCH v4 24/27] mm/mmap: Create a guard area between VMAs

On Wed, Oct 03, 2018 at 09:00:04AM -0700, Yu-cheng Yu wrote:
> On Tue, 2018-10-02 at 22:36 -0700, Andy Lutomirski wrote:
> > On Tue, Oct 2, 2018 at 9:55 PM Eugene Syromiatnikov <esyr@...hat.com> wrote:
> > > 
> > > On Fri, Sep 21, 2018 at 08:03:48AM -0700, Yu-cheng Yu wrote:
> > > > Create a guard area between VMAs, to detect memory corruption.
> > > 
> > > Do I understand correctly that with this patch a user space program
> > > no longer be able to place two mappings back to back? If it is so,
> > > it will likely break a lot of things; for example, it's a common ring
> > > buffer implementations technique, to map buffer memory twice back
> > > to back in order to avoid special handling of items wrapping its end.
> > 
> > I haven't checked what the patch actually does, but it shouldn't have
> > any affect on MAP_FIXED or the new no-replace MAP_FIXED variant.
> > 
> > --Andy
> 
> I did some mmap tests with/without MAP_FIXED, and it works as intended.
> In addition to the ring buffer, are there other test cases?

Right, after some more code reading I figured out that it indeed
shouldn't affect MAP_FIXED, thank you for confirmation.

I'm not sure, however, whether such a change that provides no ability
to configure or affect it will go well with all the supported
architectures.