linux-kernel - Re: [v6 PATCH 07/21] x86/insn-eval: Add utility function to get segment descriptor

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: <1494555237.118905.54.camel@ranerica-desktop>
Date:   Thu, 11 May 2017 19:13:57 -0700
From:   Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To:     Borislav Petkov <bp@...e.de>
Cc:     Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Brian Gerst <brgerst@...il.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Huang Rui <ray.huang@....com>, Jiri Slaby <jslaby@...e.cz>,
        Jonathan Corbet <corbet@....net>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Chen Yucong <slaoub@...il.com>,
        Alexandre Julliard <julliard@...ehq.org>,
        Stas Sergeev <stsp@...t.ru>, Fenghua Yu <fenghua.yu@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-msdos@...r.kernel.org, wine-devel@...ehq.org,
        Adam Buchbinder <adam.buchbinder@...il.com>,
        Colin Ian King <colin.king@...onical.com>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Qiaowei Ren <qiaowei.ren@...el.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Thomas Garnier <thgarnie@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [v6 PATCH 07/21] x86/insn-eval: Add utility function to get
 segment descriptor

On Thu, 2017-05-04 at 13:02 +0200, Borislav Petkov wrote:
> 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?
> 

Sure I can. Would this trigger a v8 of my series? I was hoping v7 series
could be merged and then start doing incremental work on top of it. Does
it make sense?

Thanks and BR,
Ricardo