linux-kernel - Re: [PATCH v3 36/37] x86/cet/shstk: Add ARCH_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: <Y3QCwOJ6Soqnecrt@hirez.programming.kicks-ass.net>
Date:   Tue, 15 Nov 2022 22:21:04 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "bsingharora@...il.com" <bsingharora@...il.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "Syromiatnikov, Eugene" <esyr@...hat.com>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Eranian, Stephane" <eranian@...gle.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>,
        "rppt@...ux.ibm.com" <rppt@...ux.ibm.com>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "kcc@...gle.com" <kcc@...gle.com>, "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>,
        "pavel@....cz" <pavel@....cz>, "arnd@...db.de" <arnd@...db.de>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mike.kravetz@...cle.com" <mike.kravetz@...cle.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "jamorris@...ux.microsoft.com" <jamorris@...ux.microsoft.com>,
        "rppt@...nel.org" <rppt@...nel.org>,
        "john.allen@....com" <john.allen@....com>,
        "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>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 36/37] x86/cet/shstk: Add ARCH_CET_UNLOCK

On Tue, Nov 15, 2022 at 01:00:40PM -0800, Dave Hansen wrote:
> On 11/15/22 12:57, Peter Zijlstra wrote:
> > On Tue, Nov 15, 2022 at 08:01:12PM +0000, Edgecombe, Rick P wrote:
> >>>> +	if (task != current) {
> >>>> +		if (option == ARCH_CET_UNLOCK &&
> >>>> IS_ENABLED(CONFIG_CHECKPOINT_RESTORE)) {
> >>> Why make this conditional on CRIU at all?
> >> Kees asked for it, I think he was worried about attackers using it to
> >> unlock and disable shadow stack. So wanted to lock it down to the
> >> maximum.
> > Well, distros will all have this stuff enabled no? So not much
> > protection in practise.
> 
> Yeah, that's true for the distros.
> 
> But, I would imagine that our more paranoid friends like the ChromeOS
> folks might appreciate this.

ptrace can modify text, I'm not sure what if anything we're protecting
against.