[PATCH 0/7] vfio: mmap()/mprotect() hygiene for MMIO region mappings

[Abdifatah Suruur <suruurism@gmail.com>]

These seven patches are hygiene/hardening cleanups of the MMIO region
mmap() paths in vfio-platform, vfio/fsl-mc and vfio/cdx, all in the
same class as commit a5edadbae57e ("ptp: vmclock: prevent read-only
mappings from becoming writable").  They do two things:

 1. Clear VM_MAYWRITE on regions without VFIO_REGION_INFO_FLAG_WRITE
    so that mprotect() cannot upgrade a read-only MMIO mapping to
    writable (patches 1-3).

 2. Keep vma->vm_pgoff in the logical VFIO offset space instead of
    overwriting it with the physical frame number, and reject
    non-shared mmaps where the remap_pfn_range() COW special case
    would overwrite it anyway (patches 4-7).

Proper scoping: no in-tree platform, fsl-mc or cdx device currently
publishes a region without the WRITE flag, and none of the three
drivers calls unmap_mapping_range(), so none of these issues is
reachable today.  The vm_pgoff changes preserve the documented VFIO
core contract that every device mmap is linked to the device inode's
i_mapping so it can be revoked; that shared namespace came from
commit b7c5e64fecfa ("vfio: Create vfio_fs_type with inode per device"), so
Fixes: tags were dropped from patches 4-7 and kept on patches 1-3,
pointing at the commits that added each driver's MMIO mmap support.

Previously posted as standalone patches; grouping them into one series
per Alex's request.  Reviewed-by tags from those reviews are carried
on the affected patches.

Abdifatah Suruur (7):
  vfio/platform: prevent read-only region mappings from becoming
    writable
  vfio/fsl-mc: prevent read-only region mappings from becoming
    writable
  vfio/cdx: prevent read-only region mappings from becoming writable
  vfio/platform: keep logical vm_pgoff in MMIO region mmap
  vfio/fsl-mc: keep logical vm_pgoff in MMIO region mmap
  vfio/cdx: keep logical vm_pgoff in MMIO region mmap
  vfio/cdx: reject non-shared MMIO mmaps

 drivers/vfio/cdx/main.c                      | 11 +++++++++--
 drivers/vfio/fsl-mc/vfio_fsl_mc.c            |  9 ++++++---
 drivers/vfio/platform/vfio_platform_common.c | 15 +++++++++------
 3 files changed, 24 insertions(+), 11 deletions(-)