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From: Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>
To: Alex Williamson
	<alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
	Joerg Roedel <jroedel-l3A5Bk7waGM@public.gmane.org>,
	Jiang Liu <jiang.liu-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>,
	James Smart <jsmart2021-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: kernel BUG at drivers/iommu/intel-iommu.c:608
Date: Mon, 08 Apr 2019 08:30:27 -0700	[thread overview]
Message-ID: <1554737427.118779.271.camel@acm.org> (raw)
In-Reply-To: <20190408092345.01751472-hfcDOgR9qeA@public.gmane.org>

On Mon, 2019-04-08 at 09:23 -0600, Alex Williamson wrote:
> Loading modules is privileged:
> 
> $ modprobe vfio-pci
> modprobe: ERROR: could not insert 'vfio_pci': Operation not permitted
> 
> Granting a device to a user for device assignment purposes is also a
> privileged operation.  Can you describe a scenario where this is
> reachable without elevated privileges?  The driver core maintainer has
> indicated previously that manipulation of driver binding is effectively
> at your own risk.  It's entirely possible to bind devices to the wrong
> driver creating all sorts of bad behavior.  In this case, it appears
> that the system has been improperly configured if devices from a user
> owned group can accidentally be bound to host drivers. 

No user space action should ever crash the kernel, whether or not it
is a privileged action and whether or not a configuration mistake is
involved. The only exception are actions that are intended to crash
the kernel, e.g. SysRq-c. I'm surprised that I have to explain this.

Bart.

WARNING: multiple messages have this Message-ID (diff)
From: Bart Van Assche <bvanassche@acm.org>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: iommu@lists.linux-foundation.org, Joerg Roedel <jroedel@suse.de>,
	Jiang Liu <jiang.liu@linux.intel.com>,
	James Smart <jsmart2021@gmail.com>
Subject: Re: kernel BUG at drivers/iommu/intel-iommu.c:608
Date: Mon, 08 Apr 2019 08:30:27 -0700	[thread overview]
Message-ID: <1554737427.118779.271.camel@acm.org> (raw)
Message-ID: <20190408153027.4JWySmZaP8DT3Lfe-RoXcXaGgn4S9p8YQxOP9FhZbbw@z> (raw)
In-Reply-To: <20190408092345.01751472@x1.home>

On Mon, 2019-04-08 at 09:23 -0600, Alex Williamson wrote:
> Loading modules is privileged:
> 
> $ modprobe vfio-pci
> modprobe: ERROR: could not insert 'vfio_pci': Operation not permitted
> 
> Granting a device to a user for device assignment purposes is also a
> privileged operation.  Can you describe a scenario where this is
> reachable without elevated privileges?  The driver core maintainer has
> indicated previously that manipulation of driver binding is effectively
> at your own risk.  It's entirely possible to bind devices to the wrong
> driver creating all sorts of bad behavior.  In this case, it appears
> that the system has been improperly configured if devices from a user
> owned group can accidentally be bound to host drivers. 

No user space action should ever crash the kernel, whether or not it
is a privileged action and whether or not a configuration mistake is
involved. The only exception are actions that are intended to crash
the kernel, e.g. SysRq-c. I'm surprised that I have to explain this.

Bart.
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  parent reply	other threads:[~2019-04-08 15:30 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-07 19:10 kernel BUG at drivers/iommu/intel-iommu.c:608 Bart Van Assche
2019-04-07 19:10 ` Bart Van Assche
     [not found] ` <a523ea10-3dab-fa2c-1ecf-5cf32077565f-HInyCGIudOg@public.gmane.org>
2019-04-07 21:06   ` Alex Williamson
2019-04-07 21:06     ` Alex Williamson
     [not found]     ` <20190407150650.060cc508-hfcDOgR9qeA@public.gmane.org>
2019-04-07 23:02       ` Bart Van Assche
2019-04-07 23:02         ` Bart Van Assche
     [not found]         ` <8d876549-21da-e027-0157-8737b10e26f8-HInyCGIudOg@public.gmane.org>
2019-04-07 23:31           ` Alex Williamson
2019-04-07 23:31             ` Alex Williamson
     [not found]             ` <20190407173132.24032810-hfcDOgR9qeA@public.gmane.org>
2019-04-08 15:13               ` Bart Van Assche
2019-04-08 15:13                 ` Bart Van Assche
     [not found]                 ` <1554736414.118779.265.camel-HInyCGIudOg@public.gmane.org>
2019-04-08 15:23                   ` Alex Williamson
2019-04-08 15:23                     ` Alex Williamson
     [not found]                     ` <20190408092345.01751472-hfcDOgR9qeA@public.gmane.org>
2019-04-08 15:30                       ` Bart Van Assche [this message]
2019-04-08 15:30                         ` Bart Van Assche
2019-04-08 15:55                       ` Christoph Hellwig
2019-04-08 15:55                         ` Christoph Hellwig
2019-04-08 17:10                       ` Robin Murphy
2019-04-08 17:10                         ` Robin Murphy
     [not found]                         ` <c5511683-9739-9c74-418b-cf2aed6b294a-5wv7dgnIgG8@public.gmane.org>
2019-04-08 18:05                           ` Alex Williamson
2019-04-08 18:05                             ` Alex Williamson

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