linux-kernel - Re: [Xen-devel] [PATCH v5 0/4] x86: modify_ldt improvement, test, and config option

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Message-ID: <55BA5173.401@oracle.com>
Date:	Thu, 30 Jul 2015 12:31:47 -0400
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Andrew Cooper <andrew.cooper3@...rix.com>,
	Borislav Petkov <bp@...en8.de>
CC:	"security@...nel.org" <security@...nel.org>,
	Jan Beulich <jbeulich@...e.com>,
	Peter Zijlstra <peterz@...radead.org>, X86 ML <x86@...nel.org>,
	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
	xen-devel <xen-devel@...ts.xen.org>,
	Andy Lutomirski <luto@...nel.org>,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: [Xen-devel] [PATCH v5 0/4] x86: modify_ldt improvement, test,
 and config option

On 07/30/2015 12:12 PM, Andrew Cooper wrote:
> On 30/07/15 17:05, Borislav Petkov wrote:
>> On Thu, Jul 30, 2015 at 11:53:34AM -0400, Boris Ostrovsky wrote:
>>> As far as Xen guests are concerned,
>>>
>>> Tested-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
>> Does that mean, this patch 1/4 fixes the 32bit issue you guys are still
>> debugging on the v4 thread? Or does that need more fixing?
>>
> I was going to say... This v5 pre-dates figuring out what was wrong with
> 32bit Xen.  v5 1/4 is still susceptible.
>
> Boris: does your Tested-by cover v5 + proposed fix?
>

Only V5, no extra changes.

And perhaps dropping aliases in xen_alloc_ldt() may be sufficient since 
with that done we will only have one mapping so a subsequent fault will 
have "correct" cr2 provided by the hypervisor (from your earlier email 
it sounded that hypervisor may have been providing incorrect cr2 if 
alias exists)

-boris
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