linux-kernel - Re: [PATCH v2 04/39] x86/cpufeatures: Enable CET CR4 bit 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]

Message-ID: <1f9e89ae13b49ffbcc947bf6bdee0303387c5cd4.camel@intel.com>
Date:   Fri, 14 Oct 2022 18:15:30 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "bp@...en8.de" <bp@...en8.de>
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>,
        "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>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "kcc@...gle.com" <kcc@...gle.com>, "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>,
        "arnd@...db.de" <arnd@...db.de>,
        "jamorris@...ux.microsoft.com" <jamorris@...ux.microsoft.com>,
        "Moreira, Joao" <joao.moreira@...el.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mike.kravetz@...cle.com" <mike.kravetz@...cle.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "Yang, Weijiang" <weijiang.yang@...el.com>,
        "john.allen@....com" <john.allen@....com>,
        "rppt@...nel.org" <rppt@...nel.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 v2 04/39] x86/cpufeatures: Enable CET CR4 bit for shadow
 stack

On Fri, 2022-10-14 at 19:12 +0200, Borislav Petkov wrote:
> On Thu, Sep 29, 2022 at 03:29:01PM -0700, Rick Edgecombe wrote:
> >   static __always_inline void setup_cet(struct cpuinfo_x86 *c)
> >   {
> > -     u64 msr = CET_ENDBR_EN;
> > +     bool kernel_ibt = HAS_KERNEL_IBT &&
> > cpu_feature_enabled(X86_FEATURE_IBT);
> 
> So I'd love it if we can get rid of that HAS_KERNEL_IBT thing and use
> the usual ifdeffery with Kconfig symbols. I wouldn't like for yet
> another HAS_XXX feature checking method to proliferate as this is the
> only one:

Andrew Cooper has suggested to create some software cpu features to
differentiate user/supervisor CET feature use. It could replace
HAS_KERNEL_IBT. Any objections to that versus Kconfig symbols?

[snip]

> cpu_feature_enabled(X86_FEATURE_IBT))
> 
> >   __noendbr void cet_disable(void)
> >   {
> > -     if (cpu_feature_enabled(X86_FEATURE_IBT))
> > -             wrmsrl(MSR_IA32_S_CET, 0);
> > +     if (!(cpu_feature_enabled(X86_FEATURE_IBT) ||
> > +           cpu_feature_enabled(X86_FEATURE_SHSTK)))
> > +             return;
> > +
> > +     wrmsrl(MSR_IA32_S_CET, 0);
> > +     wrmsrl(MSR_IA32_U_CET, 0);
> >   }
> >   
> > +
> 
> Stray newline.

Oops, will clean that up. Thanks.