From mboxrd@z Thu Jan  1 00:00:00 1970
From: Borislav Petkov <bp@suse.de>
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
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To: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>, Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>, 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>, Alexandre Julliard <julliard@winehq.org>, Stas Sergeev <stsp@list.ru>, Fenghua Yu <fenghua.yu@intel.com>, "Ravi V. Shankar" <rav>

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)
--