linux-kernel - Re: [Xen-devel] [PATCH] x86/xen: Fix 32-bit PV guests's usage of kernel

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]

Date:	Wed, 09 Apr 2014 11:38:02 -0400
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Jan Beulich <JBeulich@...e.com>
CC:	Andrew Cooper <andrew.cooper3@...rix.com>,
	David Vrabel <david.vrabel@...rix.com>,
	xen-devel@...ts.xenproject.org, srostedt@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH] x86/xen: Fix 32-bit PV guests's usage of
 kernel_stack

On 04/09/2014 11:01 AM, Jan Beulich wrote:
>>>> On 09.04.14 at 16:41, <andrew.cooper3@...rix.com> wrote:
>> The latter load however can easy fault; The arguments for %ds in
>> XSA-42/ CVE-2013-0228 applies to %{e,f,g}s as well.
> And it was only that latter operation that I pointed at.

We don't seem to reference %fs after the pop so doing the fixup (as 
David suggested) should be enough?

-boris


>
>> Furthermore, I am a little concerned about the performance impact of
>> this.  I would have thought that in most cases, %fs will already be
>> correct, at which point reloading it twice is a waste of time.
> Why would you expect %fs on the IRET path to commonly point to the
> kernel segment rather than whatever user mode wants/needs? Also, I'm
> not sure adding conditionals here wouldn't harm performance about as
> much as the save/load/restore. If anything I'd look into open coding
> GET_THREAD_INFO() without using %fs for this single case.
>
> Jan
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@...ts.xen.org
> http://lists.xen.org/xen-devel

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/