linux-kernel - Re: [PATCH v2 33/39] x86/cpufeatures: Limit shadow stack to Intel CPUs

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Message-ID: <202210032147.ED1310CEA8@keescook>
Date:   Mon, 3 Oct 2022 21:54:26 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Dave Hansen <dave.hansen@...el.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Rick Edgecombe <rick.p.edgecombe@...el.com>, 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-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...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>,
        Florian Weimer <fweimer@...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, John Allen <john.allen@....com>,
        kcc@...gle.com, eranian@...gle.com, rppt@...nel.org,
        jamorris@...ux.microsoft.com, dethoma@...rosoft.com,
        Tom Lendacky <thomas.lendacky@....com>,
        "Moger, Babu" <babu.moger@....com>
Subject: Re: [PATCH v2 33/39] x86/cpufeatures: Limit shadow stack to Intel
 CPUs

On Mon, Oct 03, 2022 at 05:09:04PM -0700, Dave Hansen wrote:
> On 10/3/22 16:57, Kees Cook wrote:
> > On Thu, Sep 29, 2022 at 03:29:30PM -0700, Rick Edgecombe wrote:
> >> Shadow stack is supported on newer AMD processors, but the kernel
> >> implementation has not been tested on them. Prevent basic issues from
> >> showing up for normal users by disabling shadow stack on all CPUs except
> >> Intel until it has been tested. At which point the limitation should be
> >> removed.
> >>
> >> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
> > So running the selftests on an AMD system is sufficient to drop this
> > patch?
> 
> Yes, that's enough.
> 
> I _thought_ the AMD folks provided some tested-by's at some point in the
> past.  But, maybe I'm confusing this for one of the other shared
> features.  Either way, I'm sure no tested-by's were dropped on purpose.
> 
> I'm sure Rick is eager to trim down his series and this would be a great
> patch to drop.  Does anyone want to make that easy for Rick?
> 
> <hint> <hint>

Hey Gustavo, Nathan, or Nick! I know y'all have some fancy AMD testing
rigs. Got a moment to spin up this series and run the selftests? :)

-- 
Kees Cook