[00/13] follow_pfn and other iomap races

Message

Daniel Vetter Oct. 7, 2020, 4:44 p.m. UTC

Hi all,

This developed from a discussion with Jason, starting with some patches
touching get_vaddr_frame that I typed up.

The problem is that way back VM_IO | VM_PFNMAP mappings were pretty
static, and so just following the ptes to derive a pfn and then use that
somewhere else was ok.

But we're no longer in such a world, there's tons of little races and some
fundamental problems.

This series here is an attempt to at least scope the problem, it's all the
issues I've found with quite some code reading all over the tree:
- first part tries to move mm/frame-vector.c away, it's fundamentally an
  unsafe thing
- two patches to close follow_pfn races by holding pt locks
- two pci patches where I spotted inconsinstencies between the 3 different
  ways userspace can map pci bars
- and finally some patches to mark up the remaining issue

No testing beyond "it compiles", this is very much an rfc to figure out
whether this makes sense, whether it's a real thing, and how to fix this
up properly.

Cheers, Daniel

Daniel Vetter (13):
  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
  s390/pci: Remove races against pte updates
  PCI: obey iomem restrictions for procfs mmap
  PCI: revoke mappings like devmem
  mm: add unsafe_follow_pfn
  media/videbuf1|2: Mark follow_pfn usage as unsafe
  vfio/type1: Mark follow_pfn as unsafe

 arch/s390/pci/pci_mmio.c                      | 98 +++++++++++--------
 drivers/char/mem.c                            | 16 ++-
 drivers/gpu/drm/exynos/Kconfig                |  1 -
 drivers/gpu/drm/exynos/exynos_drm_g2d.c       | 49 +++++-----
 drivers/media/common/videobuf2/Kconfig        |  1 -
 drivers/media/common/videobuf2/Makefile       |  1 +
 .../media/common/videobuf2}/frame_vector.c    | 40 +++-----
 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   |  3 +-
 drivers/misc/habanalabs/common/memory.c       | 52 +++++-----
 drivers/pci/mmap.c                            |  3 +
 drivers/pci/proc.c                            |  5 +
 drivers/vfio/vfio_iommu_type1.c               |  4 +-
 include/linux/ioport.h                        |  2 +
 include/linux/mm.h                            | 47 +--------
 include/media/videobuf2-core.h                | 42 ++++++++
 mm/Kconfig                                    |  3 -
 mm/Makefile                                   |  1 -
 mm/memory.c                                   | 76 +++++++++++++-
 mm/nommu.c                                    | 17 ++++
 security/Kconfig                              | 13 +++
 23 files changed, 296 insertions(+), 182 deletions(-)
 rename {mm => drivers/media/common/videobuf2}/frame_vector.c (90%)