Date: Wed, 6 Sep 2017 17:44:22 +0200
From: Borislav Petkov <bp@suse.de>
To: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Brian Gerst <brgerst@gmail.com>, Chris Metcalf <cmetcalf@mellanox.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Masami Hiramatsu <mhiramat@kernel.org>, Huang Rui <ray.huang@amd.com>,
        Jiri Slaby <jslaby@suse.cz>, Jonathan Corbet <corbet@lwn.net>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Paul Gortmaker <paul.gortmaker@windriver.com>,
        Vlastimil Babka <vbabka@suse.cz>, Chen Yucong <slaoub@gmail.com>,
        "Ravi V. Shankar" <ravi.v.shankar@intel.com>,
        Shuah Khan <shuah@kernel.org>, linux-kernel@vger.kernel.org,
        x86@kernel.org, ricardo.neri@intel.com,
        Adam Buchbinder <adam.buchbinder@gmail.com>,
        Colin Ian King <colin.king@canonical.com>,
        Lorenzo Stoakes <lstoakes@gmail.com>,
        Qiaowei Ren <qiaowei.ren@intel.com>,
        Nathan Howard <liverlint@gmail.com>,
        Adan Hawthorn <adanhawthorn@gmail.com>, Joe Perches <joe@perches.com>
Subject: Re: [PATCH v8 07/28] x86/mpx: Do not use SIB.base if its value is
 101b and ModRM.mod = 0
Message-ID: <20170906154422.ywgm7m3clsfufg6y@pd.tnic>
References: <20170819002809.111312-1-ricardo.neri-calderon@linux.intel.com>
 <20170819002809.111312-8-ricardo.neri-calderon@linux.intel.com>
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On Fri, Aug 18, 2017 at 05:27:48PM -0700, Ricardo Neri wrote:
> Section 2.2.1.2 of the Intel 64 and IA-32 Architectures Software
> Developer's Manual volume 2A states that if a SIB byte is used and
> SIB.base is 101b and ModRM.mod is zero, then the base part of the base
> part of the effective address computation is null. To signal this
> situation, a -EDOM error is returned to indicate callers to ignore the
> base value present in the register operand.
> 
> In this scenario, a 32-bit displacement follows the SIB byte. Displacement
> is obtained when the instruction decoder parses the operands.
> 
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
> Cc: Colin Ian King <colin.king@canonical.com>
> Cc: Lorenzo Stoakes <lstoakes@gmail.com>
> Cc: Qiaowei Ren <qiaowei.ren@intel.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Nathan Howard <liverlint@gmail.com>
> Cc: Adan Hawthorn <adanhawthorn@gmail.com>
> Cc: Joe Perches <joe@perches.com>
> Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
> Cc: x86@kernel.org
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
> ---
>  arch/x86/mm/mpx.c | 28 +++++++++++++++++++---------
>  1 file changed, 19 insertions(+), 9 deletions(-)

Reviewed-by: Borislav Petkov <bp@suse.de>

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--