linux-kernel - Re: [PATCH 00/35] Shadow stacks for userspace

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] [day] [month] [year] [list]

Date:   Thu, 9 Jun 2022 21:04:34 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc:     "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>,
        "0x7f454c46@...il.com" <0x7f454c46@...il.com>,
        "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>,
        "adrian@...as.de" <adrian@...as.de>,
        "fweimer@...hat.com" <fweimer@...hat.com>,
        "nadav.amit@...il.com" <nadav.amit@...il.com>,
        "jannh@...gle.com" <jannh@...gle.com>,
        "avagin@...il.com" <avagin@...il.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>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "Lutomirski, Andy" <luto@...nel.org>,
        "bp@...en8.de" <bp@...en8.de>, "arnd@...db.de" <arnd@...db.de>,
        "Moreira, Joao" <joao.moreira@...el.com>,
        "Yang, Weijiang" <weijiang.yang@...el.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mike.kravetz@...cle.com" <mike.kravetz@...cle.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "john.allen@....com" <john.allen@....com>,
        "dave.martin@....com" <dave.martin@....com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "corbet@....net" <corbet@....net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "gorcunov@...il.com" <gorcunov@...il.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>
Subject: Re: [PATCH 00/35] Shadow stacks for userspace

On Wed, Jun 01, 2022 at 05:24:26PM +0000, Edgecombe, Rick P wrote:
> On Wed, 2022-06-01 at 11:06 +0300, Mike Rapoport wrote:
> > > Yea, having something working is really great. My only hesitancy is
> > > that, per a discussion on the LAM patchset, we are going to make
> > > this
> > > enabling API CET only (same semantics for though). I suppose the
> > > locking API arch_prctl() could still be support other arch
> > > features,
> > > but it might be a second CET only regset. It's not the end of the
> > > world.
> > 
> > The support for CET in criu is anyway experimental for now, if the
> > kernel
> > API will be slightly different in the end, we'll update criu.
> > The important things are the ability to control tracee shadow stack
> > from ptrace, the ability to map the shadow stack at fixed address and
> > the
> > ability to control the features at least from ptrace.
> > As long as we have APIs that provide those, it should be Ok.
> >  
> > > I guess the other consideration is tieing CRIU to glibc
> > > peculiarities.
> > > Like even if we fix glibc, then CRIU may not work with some other
> > > libc
> > > or app that force disables for some weird reason. Is it supposed to
> > > be
> > > libc-agnostic?
> > 
> > Actually using the ptrace to control the CET features does not tie
> > criu to
> > glibc. The current proposal for the arch_prctl() allows libc to lock
> > CET
> > features and having a ptrace call to control the lock makes criu
> > agnostic
> > to libc behaviour.
> 
> From staring at the glibc code, I'm suspicious something was weird with
> your test setup, as I don't think it should be locking. But I guess to
> be completely proper you would need to save and restore the lock state
> anyway. So, ok yea, on balance probably better to have an extra
> interface.
> 
> Should we make it a GET/SET interface?

Yes, I think so.

-- 
Sincerely yours,
Mike.