Re: [PATCH v7 00/17] follow_pfn and other iomap races

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Nov 27, 2020 at 05:41:14PM +0100, Daniel Vetter wrote:
> Hi all
> 
> Another update of my patch series to clamp down a bunch of races and gaps
> around follow_pfn and other access to iomem mmaps. Previous version:
> 
> v1: https://lore.kernel.org/dri-devel/20201007164426.1812530-1-daniel.vetter@ffwll.ch/
> v2: https://lore.kernel.org/dri-devel/20201009075934.3509076-1-daniel.vetter@ffwll.ch
> v3: https://lore.kernel.org/dri-devel/20201021085655.1192025-1-daniel.vetter@ffwll.ch/
> v4: https://lore.kernel.org/dri-devel/20201026105818.2585306-1-daniel.vetter@ffwll.ch/
> v5: https://lore.kernel.org/dri-devel/20201030100815.2269-1-daniel.vetter@ffwll.ch/
> v6: https://lore.kernel.org/dri-devel/20201119144146.1045202-1-daniel.vetter@ffwll.ch/
> 
> And the discussion that sparked this journey:
> 
> https://lore.kernel.org/dri-devel/20201007164426.1812530-1-daniel.vetter@ffwll.ch/
> 
> I think the first 12 patches are ready for landing. The parts starting
> with "mm: Add unsafe_follow_pfn" probably need more baking time.
> 
> Andrew, can you please pick these up, or do you prefer I do a topic branch
> and send them to Linus directly in the next merge window?
> 
> Changes in v7:
> - more acks/reviews
> - reordered with the ready pieces at the front
> - simplified the new follow_pfn function as Jason suggested
> 
> Changes in v6:
> - Tested v4l userptr as Tomasz suggested. No boom observed
> - Added RFC for locking down follow_pfn, per discussion with Christoph and
>   Jason.
> - Explain why pup_fast is safe in relevant patches, there was a bit a
>   confusion when discussing v5.
> - Fix up the resource patch, with CONFIG_IO_STRICT_DEVMEM it crashed on
>   boot due to an unintended change (reported by John)
> 
> Changes in v5:
> - Tomasz found some issues in the media patches
> - Polish suggested by Christoph for the unsafe_follow_pfn patch
> 
> Changes in v4:
> - Drop the s390 patch, that was very stand-alone and now queued up to land
>   through s390 trees.
> - Comment polish per Dan's review.
> 
> Changes in v3:
> - Bunch of polish all over, no functional changes aside from one barrier
>   in the resource code, for consistency.
> - A few more r-b tags.
> 
> Changes in v2:
> - tons of small polish&fixes all over, thanks to all the reviewers who
>   spotted issues
> - I managed to test at least the generic_access_phys and pci mmap revoke
>   stuff with a few gdb sessions using our i915 debug tools (hence now also
>   the drm/i915 patch to properly request all the pci bar regions)
> - reworked approach for the pci mmap revoke: Infrastructure moved into
>   kernel/resource.c, address_space mapping is now set up at open time for
>   everyone (which required some sysfs changes). Does indeed look a lot
>   cleaner and a lot less invasive than I feared at first.
> 
> Coments and review on the remaining bits very much welcome, especially
> from the kvm and vfio side.
> 
> Cheers, Daniel
> 
> Daniel Vetter (17):
>   drm/exynos: Stop using frame_vector helpers
>   drm/exynos: Use FOLL_LONGTERM for g2d cmdlists
>   misc/habana: Stop using frame_vector helpers
>   misc/habana: Use FOLL_LONGTERM for userptr
>   mm/frame-vector: Use FOLL_LONGTERM
>   media: videobuf2: Move frame_vector into media subsystem
>   mm: Close race in generic_access_phys
>   PCI: Obey iomem restrictions for procfs mmap
>   /dev/mem: Only set filp->f_mapping
>   resource: Move devmem revoke code to resource framework
>   sysfs: Support zapping of binary attr mmaps
>   PCI: Revoke mappings like devmem

As Jason suggested, I've pulled the first 1 patches into a topic branch.

Stephen, can you please add the below to linux-next for the 5.12 merge
window?

git://anongit.freedesktop.org/drm/drm topic/iomem-mmap-vs-gup

Once this part has landed I'll see what to do with the below part.

Thanks, Daniel

>   mm: Add unsafe_follow_pfn
>   media/videobuf1|2: Mark follow_pfn usage as unsafe
>   vfio/type1: Mark follow_pfn as unsafe
>   kvm: pass kvm argument to follow_pfn callsites
>   mm: add mmu_notifier argument to follow_pfn
> 
>  arch/powerpc/kvm/book3s_64_mmu_hv.c           |   2 +-
>  arch/powerpc/kvm/book3s_64_mmu_radix.c        |   2 +-
>  arch/powerpc/kvm/e500_mmu_host.c              |   2 +-
>  arch/x86/kvm/mmu/mmu.c                        |   8 +-
>  drivers/char/mem.c                            |  86 +-------------
>  drivers/gpu/drm/exynos/Kconfig                |   1 -
>  drivers/gpu/drm/exynos/exynos_drm_g2d.c       |  48 ++++----
>  drivers/media/common/videobuf2/Kconfig        |   1 -
>  drivers/media/common/videobuf2/Makefile       |   1 +
>  .../media/common/videobuf2}/frame_vector.c    |  57 ++++-----
>  .../media/common/videobuf2/videobuf2-memops.c |   3 +-
>  drivers/media/platform/omap/Kconfig           |   1 -
>  drivers/media/v4l2-core/videobuf-dma-contig.c |   2 +-
>  drivers/misc/habanalabs/Kconfig               |   1 -
>  drivers/misc/habanalabs/common/habanalabs.h   |   6 +-
>  drivers/misc/habanalabs/common/memory.c       |  52 +++-----
>  drivers/pci/pci-sysfs.c                       |   4 +
>  drivers/pci/proc.c                            |   6 +
>  drivers/vfio/vfio_iommu_type1.c               |   4 +-
>  fs/sysfs/file.c                               |  11 ++
>  include/linux/ioport.h                        |   6 +-
>  include/linux/kvm_host.h                      |   9 +-
>  include/linux/mm.h                            |  50 +-------
>  include/linux/sysfs.h                         |   2 +
>  include/media/frame_vector.h                  |  47 ++++++++
>  include/media/videobuf2-core.h                |   1 +
>  kernel/resource.c                             |  98 ++++++++++++++-
>  mm/Kconfig                                    |   3 -
>  mm/Makefile                                   |   1 -
>  mm/memory.c                                   | 112 +++++++++++++++---
>  mm/nommu.c                                    |  16 ++-
>  security/Kconfig                              |  13 ++
>  virt/kvm/kvm_main.c                           |  56 +++++----
>  33 files changed, 413 insertions(+), 299 deletions(-)
>  rename {mm => drivers/media/common/videobuf2}/frame_vector.c (84%)
>  create mode 100644 include/media/frame_vector.h
> 
> -- 
> 2.29.2
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch