From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752589AbdEDLCp (ORCPT ); Thu, 4 May 2017 07:02:45 -0400 Received: from mx2.suse.de ([195.135.220.15]:43318 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751799AbdEDLCm (ORCPT ); Thu, 4 May 2017 07:02:42 -0400 Date: Thu, 4 May 2017 13:02:30 +0200 From: Borislav Petkov To: Ricardo Neri , Andy Lutomirski Cc: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Peter Zijlstra , Andrew Morton , Brian Gerst , Chris Metcalf , Dave Hansen , Paolo Bonzini , Masami Hiramatsu , Huang Rui , Jiri Slaby , Jonathan Corbet , "Michael S. Tsirkin" , Paul Gortmaker , Vlastimil Babka , Chen Yucong , Alexandre Julliard , Stas Sergeev , Fenghua Yu , "Ravi V. Shankar" , Shuah Khan , linux-kernel@vger.kernel.org, x86@kernel.org, linux-msdos@vger.kernel.org, wine-devel@winehq.org, Adam Buchbinder , Colin Ian King , Lorenzo Stoakes , Qiaowei Ren , Arnaldo Carvalho de Melo , Adrian Hunter , Kees Cook , Thomas Garnier , Dmitry Vyukov Subject: Re: [v6 PATCH 07/21] x86/insn-eval: Add utility function to get segment descriptor Message-ID: <20170504110213.guyhxsomgu4iaurj@pd.tnic> References: <20170308003254.27833-1-ricardo.neri-calderon@linux.intel.com> <20170308003254.27833-8-ricardo.neri-calderon@linux.intel.com> <20170419102636.chx5fwofysehy3yx@pd.tnic> <1493243515.36058.63.camel@ranerica-desktop> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1493243515.36058.63.camel@ranerica-desktop> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 26, 2017 at 02:51:56PM -0700, Ricardo Neri wrote: > > > + seg >= current->active_mm->context.ldt->size)) { > > > > ldt->size is the size of the descriptor table but you've shifted seg by > > 3. That selector index is shifted by 3 (to the left) to form an offset > > into the descriptor table because the entries there are 8 bytes. > > I double-checked the ldt code and it seems to me that size refers to the > number of entries in the table; it is always multiplied by > LDT_ENTRY_SIZE [1], [2]. Am I missing something? No, you're not. I fell into that wrongly named struct member trap. So ldt_struct.size should actually be called ldt_struct.n_entries or similar. Because what's in there is now is not "size". And then code like new_ldt->size * LDT_ENTRY_SIZE would make much more sense if written like this: new_ldt->n_entries * LDT_ENTRY_SIZE Would you fix that in a prepatch pls? Thanks. -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) -- From mboxrd@z Thu Jan 1 00:00:00 1970 From: Borislav Petkov Subject: Re: [v6 PATCH 07/21] x86/insn-eval: Add utility function to get segment descriptor Date: Thu, 4 May 2017 13:02:30 +0200 Message-ID: <20170504110213.guyhxsomgu4iaurj@pd.tnic> References: <20170308003254.27833-1-ricardo.neri-calderon@linux.intel.com> <20170308003254.27833-8-ricardo.neri-calderon@linux.intel.com> <20170419102636.chx5fwofysehy3yx@pd.tnic> <1493243515.36058.63.camel@ranerica-desktop> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <1493243515.36058.63.camel@ranerica-desktop> Sender: linux-msdos-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="utf-8" To: Ricardo Neri , Andy Lutomirski Cc: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Peter Zijlstra , Andrew Morton , Brian Gerst , Chris Metcalf , Dave Hansen , Paolo Bonzini , Masami Hiramatsu , Huang Rui , Jiri Slaby , Jonathan Corbet , "Michael S. Tsirkin" , Paul Gortmaker , Vlastimil Babka , Chen Yucong , Alexandre Julliard , Stas Sergeev , Fenghua Yu , "Ravi V. Shankar" On Wed, Apr 26, 2017 at 02:51:56PM -0700, Ricardo Neri wrote: > > > + seg >= current->active_mm->context.ldt->size)) { > > > > ldt->size is the size of the descriptor table but you've shifted seg by > > 3. That selector index is shifted by 3 (to the left) to form an offset > > into the descriptor table because the entries there are 8 bytes. > > I double-checked the ldt code and it seems to me that size refers to the > number of entries in the table; it is always multiplied by > LDT_ENTRY_SIZE [1], [2]. Am I missing something? No, you're not. I fell into that wrongly named struct member trap. So ldt_struct.size should actually be called ldt_struct.n_entries or similar. Because what's in there is now is not "size". And then code like new_ldt->size * LDT_ENTRY_SIZE would make much more sense if written like this: new_ldt->n_entries * LDT_ENTRY_SIZE Would you fix that in a prepatch pls? Thanks. -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --