From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <JBeulich@suse.com>,
xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH 2/2] x86: don't allow clearing of TF_kernel_mode for other than 64-bit PV
Date: Wed, 31 May 2017 12:08:47 +0100 [thread overview]
Message-ID: <3b460974-c07c-441b-c4ce-9d0b8385dd8c@citrix.com> (raw)
In-Reply-To: <592E899A020000780015DF82@prv-mh.provo.novell.com>
On 31/05/17 08:15, Jan Beulich wrote:
> The flag is really only meant for those, both HVM and 32-bit PV tell
> kernel from user mode based on CPL/RPL. Remove the all-question-marks
> comment and let's be on the safe side here and also suppress clearing
> for 32-bit PV (this isn't a fast path after all).
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
Wouldn't it just be safer to disallow starting a 64bit PV guest in user
mode?
No real kernel would do such a thing, and keeping the corner case around
is bad from an attack-surface point of view.
~Andrew
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next prev parent reply other threads:[~2017-05-31 11:08 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-31 7:04 [PATCH 0/2] x86: XSA_214 follow-up Jan Beulich
2017-05-31 7:14 ` [PATCH 1/2] x86: limit page type width Jan Beulich
2017-05-31 10:01 ` Andrew Cooper
2017-05-31 10:09 ` Jan Beulich
2017-06-06 8:26 ` Jan Beulich
2017-05-31 7:15 ` [PATCH 2/2] x86: don't allow clearing of TF_kernel_mode for other than 64-bit PV Jan Beulich
2017-05-31 11:08 ` Andrew Cooper [this message]
2017-05-31 11:54 ` Jan Beulich
2017-07-03 14:56 ` Ping: " Jan Beulich
2017-12-04 10:15 ` Ping#2: " Jan Beulich
2017-12-04 15:11 ` Andrew Cooper
2017-12-04 17:05 ` Jan Beulich
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