linux-kernel - Re: [PATCH v6 28/41] x86: Introduce userspace API for 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:   Tue, 28 Feb 2023 22:35:38 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "bp@...en8.de" <bp@...en8.de>
CC:     "david@...hat.com" <david@...hat.com>,
        "bsingharora@...il.com" <bsingharora@...il.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "Syromiatnikov, Eugene" <esyr@...hat.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "Eranian, Stephane" <eranian@...gle.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "fweimer@...hat.com" <fweimer@...hat.com>,
        "nadav.amit@...il.com" <nadav.amit@...il.com>,
        "jannh@...gle.com" <jannh@...gle.com>,
        "dethoma@...rosoft.com" <dethoma@...rosoft.com>,
        "kcc@...gle.com" <kcc@...gle.com>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "pavel@....cz" <pavel@....cz>, "oleg@...hat.com" <oleg@...hat.com>,
        "hjl.tools@...il.com" <hjl.tools@...il.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "Yang, Weijiang" <weijiang.yang@...el.com>,
        "Lutomirski, Andy" <luto@...nel.org>,
        "jamorris@...ux.microsoft.com" <jamorris@...ux.microsoft.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Schimpe, Christina" <christina.schimpe@...el.com>,
        "mike.kravetz@...cle.com" <mike.kravetz@...cle.com>,
        "debug@...osinc.com" <debug@...osinc.com>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "andrew.cooper3@...rix.com" <andrew.cooper3@...rix.com>,
        "john.allen@....com" <john.allen@....com>,
        "rppt@...nel.org" <rppt@...nel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "corbet@....net" <corbet@....net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "gorcunov@...il.com" <gorcunov@...il.com>
Subject: Re: [PATCH v6 28/41] x86: Introduce userspace API for shadow stack

On Tue, 2023-02-28 at 11:58 +0100, Borislav Petkov wrote:
> On Fri, Feb 24, 2023 at 06:37:57PM +0000, Edgecombe, Rick P wrote:
> > In the first patch:
> > 
> > 
https://lore.kernel.org/lkml/20230218211433.26859-2-rick.p.edgecombe@intel.com/
> > 
> > Then some more documentation is added about ARCH_SHSTK_UNLOCK and
> > ARCH_SHSTK_STATUS (which are for CRIU) in those patches.
> 
> Right, I was thinking more about ARCH_PRCTL(2), the man page.
> 
> But you can send that to the manpages folks later. I.e., it should be
> nearly impossible to be missed. :)

Sure I can add something. Somewhere I have a man page for
map_shadow_stack written up as well.

> 
> > There are glibc patches prepared by HJ to use the new interface and
> > it's my understanding that he has discussed the changes with the
> > other
> > glibc folks. Those glibc patches are used for testing these kernel
> > patches, but will not get upstream until the kernel patches to
> > avoid
> > repeating the past problems. So I think it's as prepared as it can
> > be.
> 
> Good.
> 
> > One future thing that might come up... Glibc has this mode called
> > "permissive mode". When glibc is configured this way (compile time
> > or
> > env var), it is supposed to disable shadow stack when dlopen()ing
> > any
> > DSO that doesn't have the shadow stack elf header bit.
> 
> Maybe I don't understand all the possible use cases but if I were
> interested in using shadow stack, then I'd enable it for all objects.

Enabling for all objects is the ideal, but in practice distros don't
have that.

> And if I want permissive, I'd disable it for all. A mixed thing
> sounds
> like a mixed can of worms waiting to be opened.

It is definitely a can of worms.