From: Robin Murphy <robin.murphy@arm.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>,
Kevin Tian <kevin.tian@intel.com>,
Chaitanya Kulkarni <kch@nvidia.com>,
Ashok Raj <ashok.raj@intel.com>,
kvm@vger.kernel.org, rafael@kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Cornelia Huck <cohuck@redhat.com>, Will Deacon <will@kernel.org>,
linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
Alex Williamson <alex.williamson@redhat.com>,
Jacob jun Pan <jacob.jun.pan@intel.com>,
linux-pci@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
Diana Craciun <diana.craciun@oss.nxp.com>
Subject: Re: [PATCH 03/11] PCI: pci_stub: Suppress kernel DMA ownership auto-claiming
Date: Mon, 15 Nov 2021 18:44:27 +0000 [thread overview]
Message-ID: <055c0ccb-7676-8e04-9d8f-a49dc3e8fc0a@arm.com> (raw)
In-Reply-To: <YZKkl/1GN+KgjYs6@infradead.org>
On 2021-11-15 18:19, Christoph Hellwig wrote:
> On Mon, Nov 15, 2021 at 05:54:42PM +0000, Robin Murphy wrote:
>>> s/PIO/MMIO, but yes basically. And not just data trasnfer but
>>> userspace can interfere with the device state as well.
>>
>> Sure, but unexpected changes in device state could happen for any number of
>> reasons - uncorrected ECC error, surprise removal, etc. - so if that can
>> affect "kernel integrity" I'm considering it an independent problem.
>
> Well, most DMA is triggered by the host requesting it through MMIO.
> So having access to the BAR can turn many devices into somewhat
> arbitrary DMA engines.
Yup, but as far as I understand we're talking about the situation where
the overall group is already attached to the VFIO domain by virtue of
device A, so any unsolicited DMA by device B could only be to
userspace's own memory.
>> I can see the argument from that angle, but you can equally look at it
>> another way and say that a device with kernel ownership is incompatible with
>> a kernel driver, if userspace can call write() on "/sys/devices/B/resource0"
>> such that device A's kernel driver DMAs all over it. Maybe that particular
>> example lands firmly under "just don't do that", but I'd like to figure out
>> where exactly we should draw the line between "DMA" and "ability to mess
>> with a device".
>
> Userspace writing to the resourceN files with a bound driver is a mive
> receipe for trouble. Do we really allow this currently?
No idea - I just want to make sure we don't get blinkered on VFIO at
this point and consider the potential problem space fully :)
Robin.
next prev parent reply other threads:[~2021-11-15 22:55 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-15 2:05 [PATCH 00/11] Fix BUG_ON in vfio_iommu_group_notifier() Lu Baolu
2021-11-15 2:05 ` [PATCH 01/11] iommu: Add device dma ownership set/release interfaces Lu Baolu
2021-11-15 13:14 ` Christoph Hellwig
2021-11-16 1:57 ` Lu Baolu
2021-11-16 13:46 ` Jason Gunthorpe
2021-11-17 5:22 ` Lu Baolu
2021-11-17 13:35 ` Jason Gunthorpe
2021-11-18 1:12 ` Lu Baolu
2021-11-18 14:10 ` Jason Gunthorpe
2021-11-18 2:39 ` Tian, Kevin
2021-11-18 13:33 ` Jason Gunthorpe
2021-11-19 5:44 ` Tian, Kevin
2021-11-19 11:14 ` Lu Baolu
2021-11-19 15:06 ` Jörg Rödel
2021-11-19 15:43 ` Jason Gunthorpe
2021-11-20 11:16 ` Lu Baolu
2021-11-19 12:56 ` Jason Gunthorpe
2021-11-15 20:38 ` Bjorn Helgaas
2021-11-16 1:52 ` Lu Baolu
2021-11-15 2:05 ` [PATCH 02/11] driver core: Set DMA ownership during driver bind/unbind Lu Baolu
2021-11-15 6:59 ` Greg Kroah-Hartman
2021-11-15 13:20 ` Christoph Hellwig
2021-11-15 13:38 ` Jason Gunthorpe
2021-11-15 13:19 ` Christoph Hellwig
2021-11-15 13:24 ` Jason Gunthorpe
2021-11-15 15:37 ` Robin Murphy
2021-11-15 15:56 ` Jason Gunthorpe
2021-11-15 18:15 ` Christoph Hellwig
2021-11-15 18:35 ` Robin Murphy
2021-11-15 19:39 ` Jason Gunthorpe
2021-11-15 2:05 ` [PATCH 03/11] PCI: pci_stub: Suppress kernel DMA ownership auto-claiming Lu Baolu
2021-11-15 13:21 ` Christoph Hellwig
2021-11-15 13:31 ` Jason Gunthorpe
2021-11-15 15:14 ` Robin Murphy
2021-11-15 16:17 ` Jason Gunthorpe
2021-11-15 17:54 ` Robin Murphy
2021-11-15 18:19 ` Christoph Hellwig
2021-11-15 18:44 ` Robin Murphy [this message]
2021-11-15 19:22 ` Jason Gunthorpe
2021-11-15 20:58 ` Robin Murphy
2021-11-15 21:19 ` Jason Gunthorpe
2021-11-15 20:48 ` Bjorn Helgaas
2021-11-15 22:17 ` Bjorn Helgaas
2021-11-16 6:05 ` Lu Baolu
2021-11-15 2:05 ` [PATCH 04/11] PCI: portdrv: " Lu Baolu
2021-11-15 20:44 ` Bjorn Helgaas
2021-11-16 7:24 ` Lu Baolu
2021-11-16 20:22 ` Bjorn Helgaas
2021-11-16 20:48 ` Jason Gunthorpe
2021-11-15 2:05 ` [PATCH 05/11] iommu: Add security context management for assigned devices Lu Baolu
2021-11-15 13:22 ` Christoph Hellwig
2021-11-16 7:25 ` Lu Baolu
2021-11-15 2:05 ` [PATCH 06/11] iommu: Expose group variants of dma ownership interfaces Lu Baolu
2021-11-15 13:27 ` Christoph Hellwig
2021-11-16 9:42 ` Lu Baolu
2021-11-15 2:05 ` [PATCH 07/11] vfio: Use DMA_OWNER_USER to declaim passthrough devices Lu Baolu
2021-11-15 2:05 ` [PATCH 08/11] vfio: Remove use of vfio_group_viable() Lu Baolu
2021-11-15 2:05 ` [PATCH 09/11] vfio: Delete the unbound_list Lu Baolu
2021-11-15 2:05 ` [PATCH 10/11] vfio: Remove iommu group notifier Lu Baolu
2021-11-15 2:05 ` [PATCH 11/11] iommu: Remove iommu group changes notifier Lu Baolu
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