From: Paolo Bonzini <pbonzini@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>,
Jens Axboe <axboe@kernel.dk>,
linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org
Subject: Re: PING^7 (was Re: [PATCH v2 00/14] Corrections and customization of the SG_IO command whitelist (CVE-2012-4542))
Date: Fri, 24 May 2013 09:13:03 +0200 [thread overview]
Message-ID: <519F12FF.6090809@redhat.com> (raw)
In-Reply-To: <20130524014405.GB16882@mtj.dyndns.org>
Il 24/05/2013 03:44, Tejun Heo ha scritto:
> On Thu, May 23, 2013 at 11:47:25AM +0200, Paolo Bonzini wrote:
>>> No no, I'm not talking about it not working for the users - it's just
>>> passing the commands, it of course works. I'm doubting about it being
>>> a worthy security isolation layer. cdb filtering (of any form really)
>>> has always been something on the border. It always was something we
>>> got stuck with due to lack of other immediate options.
>>
>> I understood correctly then. :) I agree it's not the best, but it's not
>> completely broken either. It has bugs, and that's what these patches
>> try to fix.
>
> The same filtering table being applied to different classes of
> hardware is a software bug, but my point is that the practive
> essentially entrusts non-insignificant part of security enforcement to
> the hardware itself. The variety of hardware in question is very wide
> and significant portion has historically been known to be flaky.
Unproven theory, and contradicted by actual practice. Bugs are more
common in the handling of borderline conditions, not in the handling of
unimplemented commands.
If you want to be secure aginst buggy firmware, the commands you have to
block are READ and WRITE. Check out the list of existing USB quirks.
>>> I'm wondering whether combining 3 into 4 would be good enough.
>>
>> No, it wouldn't. I learnt it the hard way (by having a patch nacked :))
>> at http://thread.gmane.org/gmane.linux.kernel/1311887.
>
> Of course you can't do that by adding dangerous commands to the
> existing filtering table which is allowed by default. I'm saying
> "count me out" knob could be good enough. Neither is perfect but at
> least the latter doesn't affect the default cases.
You need to allow more commands.
The count-me-out knob allows all commands.
You cannot always allow all commands.
Ergo, you cannot always use the count-me-out knob.
Paolo
next prev parent reply other threads:[~2013-05-24 7:13 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-06 15:15 [PATCH v2 00/14] Corrections and customization of the SG_IO command whitelist (CVE-2012-4542) Paolo Bonzini
2013-02-06 15:15 ` [PATCH v2 01/14] sg_io: pass request_queue to blk_verify_command Paolo Bonzini
2013-02-06 15:15 ` [PATCH v2 02/14] sg_io: reorganize list of allowed commands Paolo Bonzini
2013-02-06 15:15 ` [PATCH v2 03/14] sg_io: use different default filters for each device class Paolo Bonzini
2013-02-06 15:15 ` [PATCH v2 04/14] sg_io: resolve conflicts between commands assigned to multiple classes (CVE-2012-4542) Paolo Bonzini
2013-02-06 15:15 ` [PATCH v2 05/14] sg_io: whitelist a few more commands for rare & obsolete device types Paolo Bonzini
2013-02-06 15:15 ` [PATCH v2 06/14] sg_io: whitelist another command for multimedia devices Paolo Bonzini
2013-02-06 15:15 ` [PATCH v2 07/14] sg_io: whitelist a few more commands for media changers Paolo Bonzini
2013-02-06 15:15 ` [PATCH v2 08/14] sg_io: whitelist a few more commands for tapes Paolo Bonzini
2013-02-06 15:15 ` [PATCH v2 09/14] sg_io: whitelist a few more commands for disks Paolo Bonzini
2013-02-06 15:15 ` [PATCH v2 10/14] sg_io: whitelist a few obsolete commands Paolo Bonzini
2013-02-06 15:15 ` [PATCH v2 11/14] sg_io: mark blk_set_cmd_filter_defaults as __init Paolo Bonzini
2013-02-06 15:15 ` [PATCH v2 12/14] sg_io: remove remnants of sysfs SG_IO filters Paolo Bonzini
2013-02-06 15:16 ` [PATCH v2 13/14] sg_io: introduce unpriv_sgio queue flag Paolo Bonzini
2013-02-06 15:16 ` [PATCH v2 14/14] sg_io: use unpriv_sgio to disable whitelisting for scanners Paolo Bonzini
2013-02-13 8:32 ` [PATCH v2 00/14] Corrections and customization of the SG_IO command whitelist (CVE-2012-4542) Paolo Bonzini
2013-02-13 15:35 ` Douglas Gilbert
2013-02-13 15:48 ` Paolo Bonzini
2013-02-20 16:12 ` Paolo Bonzini
2013-03-22 22:30 ` PING^2 " Paolo Bonzini
2013-04-04 18:18 ` PING^3 " Paolo Bonzini
2013-04-17 12:26 ` PING^4 aka The Jon Corbet Effect " Paolo Bonzini
2013-04-27 13:31 ` PING^5 aka New ways to attract attentions " Paolo Bonzini
2013-05-06 20:43 ` PING^6 " Paolo Bonzini
2013-05-22 6:35 ` PING^7 (was Re: [PATCH v2 00/14] Corrections and customization of the SG_IO command whitelist (CVE-2012-4542)) Paolo Bonzini
2013-05-22 9:32 ` Tejun Heo
2013-05-22 9:53 ` Paolo Bonzini
2013-05-22 10:02 ` Tejun Heo
2013-05-22 10:23 ` Paolo Bonzini
2013-05-22 12:07 ` James Bottomley
2013-05-22 14:07 ` Paolo Bonzini
2013-05-22 16:31 ` Paolo Bonzini
2013-05-22 13:41 ` Tejun Heo
2013-05-22 14:12 ` Paolo Bonzini
2013-05-22 14:30 ` Tejun Heo
2013-05-22 15:00 ` Paolo Bonzini
2013-05-22 19:30 ` Tejun Heo
2013-05-22 21:18 ` Paolo Bonzini
2013-05-22 22:17 ` Tejun Heo
2013-05-23 0:54 ` Tejun Heo
2013-05-23 7:45 ` Paolo Bonzini
2013-05-23 9:02 ` Tejun Heo
2013-05-23 9:47 ` Paolo Bonzini
2013-05-24 1:44 ` Tejun Heo
2013-05-24 7:13 ` Paolo Bonzini [this message]
2013-05-24 8:02 ` Tejun Heo
2013-05-24 8:31 ` Paolo Bonzini
2013-05-24 9:07 ` Tejun Heo
2013-05-24 9:45 ` Paolo Bonzini
2013-05-24 22:20 ` Tejun Heo
2013-05-25 4:35 ` James Bottomley
2013-05-25 5:27 ` Christoph Hellwig
2013-05-25 7:05 ` Paolo Bonzini
2013-05-25 7:11 ` Christoph Hellwig
2013-05-25 7:21 ` Paolo Bonzini
2013-06-21 11:57 ` Christoph Hellwig
2013-05-25 8:37 ` Tejun Heo
2013-05-25 11:14 ` Paolo Bonzini
2013-05-25 12:48 ` Tejun Heo
2013-05-25 12:56 ` Paolo Bonzini
2013-05-22 15:03 ` Theodore Ts'o
2013-05-22 15:53 ` Paolo Bonzini
2013-05-22 16:32 ` Martin K. Petersen
2013-05-22 17:00 ` Paolo Bonzini
2013-05-22 18:11 ` Theodore Ts'o
2013-05-22 19:37 ` Paolo Bonzini
2013-05-22 20:19 ` Theodore Ts'o
2013-05-22 20:36 ` Paolo Bonzini
2013-05-25 3:54 ` Vladislav Bolkhovitin
2013-05-28 20:25 ` Martin K. Petersen
2013-05-29 6:12 ` Vladislav Bolkhovitin
2013-05-22 20:39 ` Tejun Heo
2013-05-22 21:12 ` Paolo Bonzini
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