linux-kernel - Re: [PATCH v19 05/25] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states

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: <202102041159.44C6C3588@keescook>
Date:   Thu, 4 Feb 2021 11:59:43 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     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>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>
Subject: Re: [PATCH v19 05/25] x86/fpu/xstate: Introduce CET MSR and XSAVES
 supervisor states

On Wed, Feb 03, 2021 at 02:55:27PM -0800, Yu-cheng Yu wrote:
> Control-flow Enforcement Technology (CET) introduces these MSRs:
> 
>     MSR_IA32_U_CET (user-mode CET settings),
>     MSR_IA32_PL3_SSP (user-mode shadow stack pointer),
> 
>     MSR_IA32_PL0_SSP (kernel-mode shadow stack pointer),
>     MSR_IA32_PL1_SSP (Privilege Level 1 shadow stack pointer),
>     MSR_IA32_PL2_SSP (Privilege Level 2 shadow stack pointer),
>     MSR_IA32_S_CET (kernel-mode CET settings),
>     MSR_IA32_INT_SSP_TAB (exception shadow stack table).
> 
> The two user-mode MSRs belong to XFEATURE_CET_USER.  The first three of
> kernel-mode MSRs belong to XFEATURE_CET_KERNEL.  Both XSAVES states are
> supervisor states.  This means that there is no direct, unprivileged access
> to these states, making it harder for an attacker to subvert CET.
> 
> For sigreturn and future ptrace() support, shadow stack address and MSR
> reserved bits are checked before written to the supervisor states.
> 
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook