linux-kernel - Re: [PATCH v3 35/37] x86/cet: Add PTRACE interface for CET

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: <dcbf087fb8082be8ff9be14c440a0efaee95cf93.camel@intel.com>
Date:   Mon, 21 Nov 2022 15:52:57 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "rppt@...nel.org" <rppt@...nel.org>
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>,
        "Yu, Yu-cheng" <yu-cheng.yu@...el.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>,
        "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>,
        "bp@...en8.de" <bp@...en8.de>, "oleg@...hat.com" <oleg@...hat.com>,
        "hjl.tools@...il.com" <hjl.tools@...il.com>,
        "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>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "pavel@....cz" <pavel@....cz>,
        "john.allen@....com" <john.allen@....com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.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 v3 35/37] x86/cet: Add PTRACE interface for CET

On Mon, 2022-11-21 at 09:40 +0200, Mike Rapoport wrote:
> On Thu, Nov 17, 2022 at 07:57:59PM +0000, Edgecombe, Rick P wrote:
> > On Thu, 2022-11-17 at 12:25 +0000, Schimpe, Christina wrote:
> > > > Hmm, we definitely need to be able to set the SSP. Christina,
> > > > does
> > > > GDB need
> > > > anything else? I thought maybe toggling SHSTK_EN?
> > > 
> > > In addition to the SSP, we want to write the CET state. For
> > > instance
> > > for inferior calls,
> > > we want to reset the IBT bits.
> > > However, we won't write states that are disallowed by HW.
> > 
> > Sorry, I should have given more background. Peter is saying we
> > should
> > split the ptrace interface so that shadow stack and IBT are
> > separate. 
> > They would also no longer necessarily mirror the CET_U MSR format.
> > Instead the kernel would expose a kernel specific format that has
> > the
> > needed bits of shadow stack support. And a separate one later for
> > IBT.
> > 
> > So the question is what does shadow stack need to support for
> > ptrace
> > besides SSP? Is it only SSP? The other features are SHSTK_EN and
> > WRSS_EN. It might actually be nice to keep how these bits get
> > flipped
> > more controlled (remove them from ptrace). It looks like CRIU
> > didn't
> > need them.
> 
>  
> CRIU reads CET_U with ptrace(PTRACE_GETREGSET, NT_X86_CET). It's done
> before the injection of the parasite. The value of SHSTK_EN is used
> then to
> detect if shadow stack is enabled and to setup victim's shadow stack
> for
> sigreturn.

Hmm, can it read /proc/pid/status? It has some lines like this:
x86_Thread_features: shstk wrss
x86_Thread_features_locked: shstk wrss