linux-kernel - Re: [PATCH v2 18/39] mm: Add guard pages around a shadow stack.

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]

Date:   Mon, 10 Oct 2022 13:56:39 +0000
From:   Andrew Cooper <Andrew.Cooper3@...rix.com>
To:     Florian Weimer <fweimer@...hat.com>
CC:     Kees Cook <keescook@...omium.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        "x86@...nel.org" <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-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-api@...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>,
        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>,
        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>,
        Weijiang Yang <weijiang.yang@...el.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        "joao.moreira@...el.com" <joao.moreira@...el.com>,
        John Allen <john.allen@....com>,
        "kcc@...gle.com" <kcc@...gle.com>,
        "eranian@...gle.com" <eranian@...gle.com>,
        "rppt@...nel.org" <rppt@...nel.org>,
        "jamorris@...ux.microsoft.com" <jamorris@...ux.microsoft.com>,
        "dethoma@...rosoft.com" <dethoma@...rosoft.com>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>
Subject: Re: [PATCH v2 18/39] mm: Add guard pages around a shadow stack.

On 10/10/2022 14:40, Florian Weimer wrote:
> * Andrew Cooper:
>
>>> POSIX does not appear to require PROT_NONE mappings
>>> for the stack guard region, either.  However, the
>>> pthread_attr_setguardsize manual page pretty clearly says that it's got
>>> to be unreadable and unwriteable.  Hence my question.
>> Hmm.  If that's what the manuals say, then fine.
>>
>> But honestly, you don't get very far at all without faulting on a
>> read-only stack.
> I guess we can update the manual page proactively.  It does look like a
> tempting optimization.

Here's one I prepared earlier, discussing getting supervisor shadow
stacks working in Xen.

http://xenbits.xen.org/people/andrewcoop/Xen-CET-SS.pdf

This optimisation turned out to be very helpful by being able to put the
shadow stacks in what were previously the guard holes, meaning we didn't
actually need to allocate any more memory for the stacks.

~Andrew