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From: Pankaj Gupta <pagupta@redhat.com>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	qemu-devel@nongnu.org, linux-nvdimm@ml01.01.org,
	linux-fsdevel@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	linux-acpi@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-xfs@vger.kernel.org, jack@suse.cz, stefanha@redhat.com,
	dan j williams <dan.j.williams@intel.com>,
	riel@surriel.com, nilal@redhat.com, kwolf@redhat.com,
	pbonzini@redhat.com, zwisler@kernel.org,
	vishal l verma <vishal.l.verma@intel.com>,
	dave jiang <dave.jiang@intel.com>,
	david@redhat.com, jmoyer@redhat.com,
	xiaoguangrong eric <xiaoguangrong.eric@gmail.com>,
	hch@infradead.org, mst@redhat.com, jasowang@redhat.com,
	lcapitulino@redhat.com, imammedo@redhat.com, eblake@redhat.com,
	willy@infradead.org, tytso@mit.edu, adilger kernel <adilger.
Subject: Re: [PATCH v3 0/5] kvm "virtio pmem" device
Date: Fri, 11 Jan 2019 02:45:04 -0500 (EST)
Message-ID: <1326478078.61913951.1547192704870.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <20190110012617.GA4205@dastard>


> 
> On Wed, Jan 09, 2019 at 08:17:31PM +0530, Pankaj Gupta wrote:
> >  This patch series has implementation for "virtio pmem".
> >  "virtio pmem" is fake persistent memory(nvdimm) in guest
> >  which allows to bypass the guest page cache. This also
> >  implements a VIRTIO based asynchronous flush mechanism.
> 
> Hmmmm. Sharing the host page cache direct into the guest VM. Sounds
> like a good idea, but.....
> 
> This means the guest VM can now run timing attacks to observe host
> side page cache residency, and depending on the implementation I'm
> guessing that the guest will be able to control host side page
> cache eviction, too (e.g. via discard or hole punch operations).

Not sure how? this is similar to mmapping virtual memory by any userspace 
process. Any host userspace process can do such attack on host page cache
using mincore & mmap shared file. 

But i don't think guest can do this alone. For virtio-pmem usecase guest 
won't be using page cache so timing attack from only guest side is not 
possible unless host userspace can run checks on page cache eviction state
using mincore etc. 

As rightly described by Rik, guest will only access its own page cache pages 
and if guest page cache is managed directly by host, this saves alot of 
effort for guest in transferring guest state of page cache.  

> 
> Which means this functionality looks to me like a new vector for
> information leakage into and out of the guest VM via guest
> controlled host page cache manipulation.
> 
> https://arxiv.org/pdf/1901.01161
> 
> I might be wrong, but if I'm not we're going to have to be very
> careful about how guest VMs can access and manipulate host side
> resources like the page cache.....

If I am following correctly the discussions in MM thread. 
Important steps to mitigate this:

* Avoid running mincore in privilege mode: to safeguard page evict state of any 
  page cache page.
* tweaking RWF_NOWAIT 

I think if we secure ways to find current state(cached/evicted) of a page in host, 
we should be able to mitigate the impact for any page cache page access attack 
including virtio-pmem.

Thanks,
Pankaj

From: Pankaj Gupta <pagupta@redhat.com>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	qemu-devel@nongnu.org, linux-nvdimm@ml01.01.org,
	linux-fsdevel@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	linux-acpi@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-xfs@vger.kernel.org, jack@suse.cz, stefanha@redhat.com,
	dan j williams <dan.j.williams@intel.com>,
	riel@surriel.com, nilal@redhat.com, kwolf@redhat.com,
	pbonzini@redhat.com, zwisler@kernel.org,
	vishal l verma <vishal.l.verma@intel.com>,
	dave jiang <dave.jiang@intel.com>,
	david@redhat.com, jmoyer@redhat.com,
	xiaoguangrong eric <xiaoguangrong.eric@gmail.com>,
	hch@infradead.org, mst@redhat.com, jasowang@redhat.com,
	lcapitulino@redhat.com, imammedo@redhat.com, eblake@redhat.com,
	willy@infradead.org, tytso@mit.edu,
	adilger kernel <adilger.kernel@dilger.ca>,
	darrick wong <darrick.wong@oracle.com>,
	rjw@rjwysocki.net
Subject: Re: [PATCH v3 0/5] kvm "virtio pmem" device
Date: Fri, 11 Jan 2019 02:45:04 -0500 (EST)
Message-ID: <1326478078.61913951.1547192704870.JavaMail.zimbra@redhat.com> (raw)
Message-ID: <20190111074504.uO1AFkPTkFCbgnAwRiV-KdlcuwISMrYyVrTfcJtlBlA@z> (raw)
In-Reply-To: <20190110012617.GA4205@dastard>


> 
> On Wed, Jan 09, 2019 at 08:17:31PM +0530, Pankaj Gupta wrote:
> >  This patch series has implementation for "virtio pmem".
> >  "virtio pmem" is fake persistent memory(nvdimm) in guest
> >  which allows to bypass the guest page cache. This also
> >  implements a VIRTIO based asynchronous flush mechanism.
> 
> Hmmmm. Sharing the host page cache direct into the guest VM. Sounds
> like a good idea, but.....
> 
> This means the guest VM can now run timing attacks to observe host
> side page cache residency, and depending on the implementation I'm
> guessing that the guest will be able to control host side page
> cache eviction, too (e.g. via discard or hole punch operations).

Not sure how? this is similar to mmapping virtual memory by any userspace 
process. Any host userspace process can do such attack on host page cache
using mincore & mmap shared file. 

But i don't think guest can do this alone. For virtio-pmem usecase guest 
won't be using page cache so timing attack from only guest side is not 
possible unless host userspace can run checks on page cache eviction state
using mincore etc. 

As rightly described by Rik, guest will only access its own page cache pages 
and if guest page cache is managed directly by host, this saves alot of 
effort for guest in transferring guest state of page cache.  

> 
> Which means this functionality looks to me like a new vector for
> information leakage into and out of the guest VM via guest
> controlled host page cache manipulation.
> 
> https://arxiv.org/pdf/1901.01161
> 
> I might be wrong, but if I'm not we're going to have to be very
> careful about how guest VMs can access and manipulate host side
> resources like the page cache.....

If I am following correctly the discussions in MM thread. 
Important steps to mitigate this:

* Avoid running mincore in privilege mode: to safeguard page evict state of any 
  page cache page.
* tweaking RWF_NOWAIT 

I think if we secure ways to find current state(cached/evicted) of a page in host, 
we should be able to mitigate the impact for any page cache page access attack 
including virtio-pmem.

Thanks,
Pankaj



  parent reply index

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-09 14:47 Pankaj Gupta
2019-01-09 14:47 ` [PATCH v3 1/5] libnvdimm: nd_region flush callback support Pankaj Gupta
2019-01-09 14:47 ` [PATCH v3 2/5] virtio-pmem: Add virtio pmem driver Pankaj Gupta
2019-01-14 15:54   ` Michael S. Tsirkin
2019-01-14 15:54     ` Michael S. Tsirkin
     [not found]     ` <20190114105314-mutt-send-email-mst-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2019-01-15  6:33       ` Pankaj Gupta
2019-01-15  6:33         ` Pankaj Gupta
2019-01-09 14:47 ` [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag Pankaj Gupta
2019-01-09 14:47 ` [PATCH v3 4/5] ext4: disable map_sync for virtio pmem Pankaj Gupta
2019-01-09 14:47 ` [PATCH v3 5/5] xfs: " Pankaj Gupta
2019-01-09 14:47   ` Pankaj Gupta
2019-01-09 16:26   ` Darrick J. Wong
2019-01-09 18:08     ` Pankaj Gupta
     [not found] ` <20190109144736.17452-1-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-01-10  1:26   ` [PATCH v3 0/5] kvm "virtio pmem" device Dave Chinner
2019-01-10  1:26     ` Dave Chinner
2019-01-10  2:40     ` Rik van Riel
2019-01-10  2:40       ` Rik van Riel
2019-01-10 10:17     ` Jan Kara
2019-01-10 10:17       ` Jan Kara
     [not found]       ` <20190110101757.GC15790-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org>
2019-01-13  1:38         ` Pankaj Gupta
2019-01-13  1:38           ` Pankaj Gupta
     [not found]           ` <1354249849.63357171.1547343519970.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-01-13  1:43             ` Dan Williams
2019-01-13  1:43               ` Dan Williams
     [not found]               ` <CAPcyv4hwcgTUpgNCefCGu4DvgkYBp5b=f+hJ+FC=s5APYKoycg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2019-01-13  2:17                 ` [Qemu-devel] " Pankaj Gupta
2019-01-13  2:17                   ` Pankaj Gupta
     [not found]                   ` <540171952.63371441.1547345866585.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-01-14  9:55                     ` Jan Kara
2019-01-14  9:55                       ` Jan Kara
     [not found]                       ` <20190114095520.GC13316-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org>
2019-01-14 10:16                         ` Pankaj Gupta
2019-01-14 10:16                           ` Pankaj Gupta
2019-01-11  7:45     ` Pankaj Gupta [this message]
2019-01-11  7:45       ` Pankaj Gupta
     [not found]       ` <1326478078.61913951.1547192704870.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-01-13 23:29         ` Dave Chinner
2019-01-13 23:29           ` Dave Chinner
2019-01-13 23:38           ` Matthew Wilcox
2019-01-13 23:38             ` Matthew Wilcox
     [not found]             ` <20190113233820.GX6310-PfSpb0PWhxZc2C7mugBRk2EX/6BAtgUQ@public.gmane.org>
2019-01-14  2:50               ` Dave Chinner
2019-01-14  2:50                 ` Dave Chinner
2019-01-14  7:15               ` Pankaj Gupta
2019-01-14  7:15                 ` Pankaj Gupta
     [not found]                 ` <942065073.64011540.1547450140670.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-01-14 21:25                   ` Dave Chinner
2019-01-14 21:25                     ` Dave Chinner
2019-01-14 21:35                     ` Dan Williams
2019-01-14 21:35                       ` Dan Williams
     [not found]                       ` <CAPcyv4jtPcLV-s0sKNHwwk0ug7GLBV6699dpm1h3r2xSo879dg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2019-01-14 22:21                         ` Dave Chinner
2019-01-14 22:21                           ` Dave Chinner
2019-01-15  2:19                           ` Michael S. Tsirkin
2019-01-15  2:19                             ` Michael S. Tsirkin
     [not found]                             ` <20190114205031-mutt-send-email-mst-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2019-01-15  5:37                               ` [Qemu-devel] " Pankaj Gupta
2019-01-15  5:37                                 ` Pankaj Gupta
2019-01-15  5:35                           ` Pankaj Gupta
2019-01-15  5:35                             ` Pankaj Gupta
     [not found]                             ` <1684638419.64320214.1547530506805.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2019-01-15 20:42                               ` Dave Chinner
2019-01-15 20:42                                 ` Dave Chinner
2019-02-04 22:56 ` security implications of caching with virtio pmem (was Re: [PATCH v3 0/5] kvm "virtio pmem" device) Michael S. Tsirkin
2019-02-05  7:29   ` [Qemu-devel] " Pankaj Gupta
2019-02-06 14:00   ` David Hildenbrand
2019-02-06 18:01     ` Michael S. Tsirkin
2019-02-11  7:29   ` [Qemu-devel] " Pankaj Gupta
2019-02-11 22:29     ` Dave Chinner
2019-02-11 22:58       ` David Hildenbrand
2019-02-11 23:07         ` Michael S. Tsirkin
  -- strict thread matches above, loose matches on Subject: below --
2019-01-09 13:50 [PATCH v3 0/5] kvm "virtio pmem" device Pankaj Gupta

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