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From: George Dunlap <george.dunlap@citrix.com>
To: "Jürgen Groß" <jgross@suse.com>,
	"Jan Beulich" <jbeulich@suse.com>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>
Cc: Sergey Dyasli <sergey.dyasli@citrix.com>,
	Lars Kurth <lars.kurth@citrix.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Julien Grall <julien@xen.org>, Wei Liu <wl@xen.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	George Dunlap <George.Dunlap@eu.citrix.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>,
	xen-devel@lists.xen.org, Daniel De Graaf <dgdegra@tycho.nsa.gov>
Subject: Re: [Xen-devel] [PATCH v2] xsm: hide detailed Xen version from unprivileged guests
Date: Fri, 10 Jan 2020 17:00:36 +0000	[thread overview]
Message-ID: <feeedeb6-a70c-efe5-d270-cd4d7881c4ce@citrix.com> (raw)
In-Reply-To: <e57a35f1-1c81-8393-0efd-c3592aa69dd2@suse.com>

On 1/10/20 4:45 PM, Jürgen Groß wrote:
> On 10.01.20 16:56, Jan Beulich wrote:
>> On 10.01.2020 16:28, George Dunlap wrote:
>>> On 1/10/20 11:02 AM, Andrew Cooper wrote:
>>>> On 10/01/2020 10:37, Sergey Dyasli wrote:
>>>>> Hide the following information that can help identify the running Xen
>>>>> binary version: XENVER_extraversion, XENVER_compile_info,
>>>>> XENVER_changeset.
>>>>> Add explicit cases for XENVER_commandline and XENVER_build_id as well.
>>>>>
>>>>> Introduce xsm_filter_denied() to hvmloader to remove "<denied>" string
>>>>> from guest's DMI tables that otherwise would be shown in tools like
>>>>> dmidecode.
>>>>>
>>>>> Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com>
>>>>> ---
>>>>> v1 --> v2:
>>>>> - Added xsm_filter_denied() to hvmloader instead of modifying
>>>>> xen_deny()
>>>>> - Made behaviour the same for both Release and Debug builds
>>>>> - XENVER_capabilities is no longer hided
>>>>>
>>>>> CC: Andrew Cooper <andrew.cooper3@citrix.com>
>>>>> CC: George Dunlap <George.Dunlap@eu.citrix.com>
>>>>> CC: Ian Jackson <ian.jackson@eu.citrix.com>
>>>>> CC: Jan Beulich <jbeulich@suse.com>
>>>>> CC: Julien Grall <julien@xen.org>
>>>>> CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>>>>> CC: Stefano Stabellini <sstabellini@kernel.org>
>>>>> CC: Wei Liu <wl@xen.org>
>>>>> CC: Daniel De Graaf <dgdegra@tycho.nsa.gov>
>>>>
>>>> I realise there are arguments over how to fix this, but we (the Xen
>>>> community) have already f*cked up once here, and this is doing so a
>>>> second time.
>>>>
>>>> Nack.
>>>>
>>>> Fixing it anywhere other than Xen is simply not appropriate.
>>
>> (replying here, because the original mail doesn't seem to have
>> made it into my inbox)
>>
>> I've said so to Sergey already on v1: The "fix" you want needs to
>> be at or closer to the presentation layer. From Xen's perspective
>> the request for information was _indeed_ denied.
>>
>>>> The reason for this (which ought to be obvious, but I guess only to
>>>> those who actually do customer support) is basic human physiology.
>>>> "denied" means something has gone wrong.  It scares people, and causes
>>>> them to seek help to change fix whatever is broken.
>>>
>>> This seems like a reasonable argument that "<denied>" causes issues.
>>> But that doesn't change the fact that "" also causes issues.
>>>
>>> What about changing the string to "<build-id hidden>" or something like
>>> that?  That makes it more clear what would have been in that place, and
>>> "hidden" is a lot less scary than "denied".
>>
>> I could live with this. But (judging from the picture that was
>> provided earlier on) it would still require filtering at or close
>> to the presentation layer, and by changing the prior <denied> to
>> different and varying strings may make that job harder (albeit
>> perhaps they could look for any <...>).
> 
> I'd go with "<hidden>" or "<NIL>". "<build-id hidden>" as value for the
> build-id is similar to "LCD-display". And it will certainly not be the
> correct value for other hidden items. :-)

The idea is that in a log, if you see a buildid in context, you can
usually figure out what it is just by looking at it; i.e..:

Xen 4.13.1 8a2a24f4e1

So which is better?

1. Xen 4.13.1

2. Xen 4.13.1 <hidden>

3 Xen 4.13.1 <buildid hidden>

4 Xen 4.13.1 <NIL>

I don't like 1 or 4.  I could live with 2 I guess.

 -George

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  reply	other threads:[~2020-01-10 17:01 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-10 10:37 Sergey Dyasli
2020-01-10 11:02 ` Andrew Cooper
2020-01-10 15:28   ` George Dunlap
2020-01-10 15:56     ` Jan Beulich
2020-01-10 16:45       ` Jürgen Groß
2020-01-10 17:00         ` George Dunlap [this message]
2020-01-11  3:55     ` Doug Goldstein
2020-01-11  9:35       ` George Dunlap
2020-01-13 11:01   ` Sergey Dyasli
2020-01-10 11:09 ` Jan Beulich
2020-01-11  4:02 ` Doug Goldstein
2020-01-11  9:02   ` George Dunlap
2020-01-12 18:26     ` Doug Goldstein
2020-01-13 12:51       ` George Dunlap
2020-01-13 13:39         ` Julien Grall
2020-01-13 14:01           ` Andrew Cooper
2020-01-13 14:07             ` George Dunlap
2020-01-13 14:28               ` Julien Grall
2020-01-13 14:40         ` Andrew Cooper
2020-01-14 10:19           ` Sergey Dyasli
2020-01-13 14:52         ` Julien Grall
2020-01-13 14:01       ` Ian Jackson

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