From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753994AbeEWFEg (ORCPT ); Wed, 23 May 2018 01:04:36 -0400 Received: from gateway34.websitewelcome.com ([192.185.148.196]:30645 "EHLO gateway34.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751573AbeEWFEe (ORCPT ); Wed, 23 May 2018 01:04:34 -0400 X-Authority-Reason: nr=8 Subject: Re: [PATCH] kernel: sys: fix potential Spectre v1 To: Dan Williams Cc: Thomas Gleixner , Andrew Morton , Linux Kernel Mailing List , Alexei Starovoitov , Peter Zijlstra References: <20180515030038.GA11822@embeddedor.com> <20180515150859.1bccbd8d4543848b30fea859@linux-foundation.org> <50481b83-4c03-f354-bd11-cef7aecdd85f@embeddedor.com> <3d2e5771-c2c9-6e45-3e85-21c0bc86876e@embeddedor.com> <58df7ae3-8ef0-4f42-9ab2-b551d2ffff00@embeddedor.com> <161a0513-1029-a76c-f967-1e606081599d@embeddedor.com> From: "Gustavo A. R. Silva" Message-ID: <112349fb-837c-7b91-e256-a1c443710150@embeddedor.com> Date: Wed, 23 May 2018 00:03:57 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 187.192.46.223 X-Source-L: No X-Exim-ID: 1fLLwu-002hOH-W2 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: ([192.168.1.70]) [187.192.46.223]:32926 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 4 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/22/2018 03:50 PM, Dan Williams wrote: >>> >>> Dan, >>> >>> What do you think about this first draft: >>> >>> diff --git a/include/linux/nospec.h b/include/linux/nospec.h >>> index e791ebc..6154183 100644 >>> --- a/include/linux/nospec.h >>> +++ b/include/linux/nospec.h >>> @@ -55,4 +55,16 @@ static inline unsigned long >>> array_index_mask_nospec(unsigned long index, >>> \ >>> (typeof(_i)) (_i & _mask); \ >>> }) >>> + >>> +#define validate_index_nospec(index, size) \ >>> +({ \ >>> + typeof(index) *ptr = &(index); \ >>> + typeof(size) _s = (size); \ >>> + \ >>> + BUILD_BUG_ON(sizeof(*ptr) > sizeof(long)); \ >>> + BUILD_BUG_ON(sizeof(_s) > sizeof(long)); \ >>> + \ >>> + *ptr >= _s ? false : \ >>> + (*ptr = array_index_nospec(*ptr, _s) ? true : true); \ >> >> >> This actually should be: >> >> ((*ptr = array_index_nospec(*ptr, _s)) ? true : true); >> > > Let's not use ternary conditionals at all to make this more readable. > OK. How about this: diff --git a/include/linux/nospec.h b/include/linux/nospec.h index e791ebc..498995b 100644 --- a/include/linux/nospec.h +++ b/include/linux/nospec.h @@ -55,4 +55,21 @@ static inline unsigned long array_index_mask_nospec(unsigned long index, \ (typeof(_i)) (_i & _mask); \ }) + +#define validate_index_nospec(index, size) \ +({ \ + bool ret = true; \ + typeof(index) *ptr = &(index); \ + typeof(size) _s = (size); \ + \ + BUILD_BUG_ON(sizeof(*ptr) > sizeof(long)); \ + BUILD_BUG_ON(sizeof(_s) > sizeof(long)); \ + \ + if (*ptr >= size) \ + ret = false; \ + \ + *ptr = array_index_nospec(*ptr, _s); \ + \ + ret; \ +}) #endif /* _LINUX_NOSPEC_H */ Thanks -- Gustavo