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From: Jason Gunthorpe <jgg@ziepe.ca>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "DRI Development" <dri-devel@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>,
	kvm@vger.kernel.org, linux-mm@kvack.org,
	linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org,
	linux-s390@vger.kernel.org,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"John Hubbard" <jhubbard@nvidia.com>,
	"Jérôme Glisse" <jglisse@redhat.com>, "Jan Kara" <jack@suse.cz>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	linux-pci@vger.kernel.org,
	"Daniel Vetter" <daniel.vetter@ffwll.com>
Subject: Re: [PATCH v3 12/16] PCI: Obey iomem restrictions for procfs mmap
Date: Wed, 21 Oct 2020 09:50:30 -0300	[thread overview]
Message-ID: <20201021125030.GK36674@ziepe.ca> (raw)
In-Reply-To: <20201021085655.1192025-13-daniel.vetter@ffwll.ch>

On Wed, Oct 21, 2020 at 10:56:51AM +0200, Daniel Vetter wrote:
> There's three ways to access PCI BARs from userspace: /dev/mem, sysfs
> files, and the old proc interface. Two check against
> iomem_is_exclusive, proc never did. And with CONFIG_IO_STRICT_DEVMEM,
> this starts to matter, since we don't want random userspace having
> access to PCI BARs while a driver is loaded and using it.
> 
> Fix this by adding the same iomem_is_exclusive() check we already have
> on the sysfs side in pci_mmap_resource().
> 
> References: 90a545e98126 ("restrict /dev/mem to idle io memory ranges")
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Cc: Jérôme Glisse <jglisse@redhat.com>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: linux-mm@kvack.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-samsung-soc@vger.kernel.org
> Cc: linux-media@vger.kernel.org
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: linux-pci@vger.kernel.org
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.com>

Maybe not for fixing in this series, but this access to
IORESOURCE_BUSY doesn't have any locking.

The write side holds the resource_lock at least..

>  	ret = pci_mmap_page_range(dev, i, vma,
>  				  fpriv->mmap_state, write_combine);

At this point the vma isn't linked into the address space, so doesn't
this happen?

     CPU 0                                  CPU1
 mmap_region()
   vma = vm_area_alloc
   proc_bus_pci_mmap
    iomem_is_exclusive
    pci_mmap_page_range
                                            revoke_devmem
                                             unmap_mapping_range()
     // vma is not linked to the address space here,
     // unmap doesn't find it
  vma_link() 
  !!! The VMA gets mapped with the revoked PTEs

I couldn't find anything that prevents it at least, no mmap_sem on the
unmap side, just the i_mmap_lock

Not seeing how address space and pre-populating during mmap work
together? Did I miss locking someplace?

Not something to be fixed for this series, this is clearly an
improvement, but seems like another problem to tackle?

Jason


  reply	other threads:[~2020-10-21 12:50 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-21  8:56 [PATCH v3 00/16] follow_pfn and other iomap races Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 01/16] drm/exynos: Stop using frame_vector helpers Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 02/16] drm/exynos: Use FOLL_LONGTERM for g2d cmdlists Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 03/16] misc/habana: Stop using frame_vector helpers Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 04/16] misc/habana: Use FOLL_LONGTERM for userptr Daniel Vetter
2020-10-23  9:12   ` Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 05/16] mm/frame-vector: Use FOLL_LONGTERM Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 06/16] media: videobuf2: Move frame_vector into media subsystem Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 07/16] mm: Close race in generic_access_phys Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 08/16] s390/pci: Remove races against pte updates Daniel Vetter
2020-10-21  9:37   ` Niklas Schnelle
2020-10-21 13:56     ` Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 09/16] mm: Add unsafe_follow_pfn Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 10/16] media/videbuf1|2: Mark follow_pfn usage as unsafe Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 11/16] vfio/type1: Mark follow_pfn " Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 12/16] PCI: Obey iomem restrictions for procfs mmap Daniel Vetter
2020-10-21 12:50   ` Jason Gunthorpe [this message]
2020-10-21 14:42     ` Daniel Vetter
2020-10-21 15:13       ` Jason Gunthorpe
2020-10-21 15:54         ` Daniel Vetter
2020-10-21 16:37           ` Jason Gunthorpe
2020-10-21 19:24             ` Daniel Vetter
2020-10-21 23:20               ` Jason Gunthorpe
2020-10-22  7:00                 ` Daniel Vetter
2020-10-22 11:43                   ` Jason Gunthorpe
2020-10-22 13:04                     ` Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 13/16] /dev/mem: Only set filp->f_mapping Daniel Vetter
2020-10-21 18:21   ` Dan Williams
2020-10-21  8:56 ` [PATCH v3 14/16] resource: Move devmem revoke code to resource framework Daniel Vetter
2020-10-21 18:59   ` Dan Williams
2020-10-21 19:25     ` Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 15/16] sysfs: Support zapping of binary attr mmaps Daniel Vetter
2020-10-21  8:56 ` [PATCH v3 16/16] PCI: Revoke mappings like devmem Daniel Vetter
2020-10-21 12:51 ` [PATCH v3 00/16] follow_pfn and other iomap races Jason Gunthorpe

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