[PATCH 6.1.y v2 0/4] fix error handling in mmap_region() and refactor (hotfixes)

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

Critical fixes for mmap_region(), backported to 6.1.y.

Some notes on differences from upstream:

* We do NOT take commit 0fb4a7ad270b ("mm: refactor
  map_deny_write_exec()"), as this refactors code only introduced in 6.2.

* We make reference in "mm: refactor arch_calc_vm_flag_bits() and arm64 MTE
  handling" to parisc, but the referenced functionality does not exist in
  this kernel.

* In this kernel is_shared_maywrite() does not exist and the code uses
  VM_SHARED to determine whether mapping_map_writable() /
  mapping_unmap_writable() should be invoked. This backport therefore
  follows suit.

* The vma_dummy_vm_ops static global doesn't exist in this kernel, so we
  use a local static variable in mmap_file() and vma_close().

* Each version of these series is confronted by a slightly different
  mmap_region(), so we must adapt the change for each stable version. The
  approach remains the same throughout, however, and we correctly avoid
  closing the VMA part way through any __mmap_region() operation.

* This version of the kernel uses mas_preallocate() rather than the
  vma_iter_prealloc() wrapper and mas_destroy() rather than the
  vma_iter_free() wrapper, however the logic of rearranging the positioning
  of these remains the same, as well as avoiding the iterator leak we
  previously had on some error paths.

v2:
* Fix 6.1-specific memory leak if second attempt at merge succeeds.

v1:
https://lore.kernel.org/all/4cb9b846f0c4efcc4a2b21453eea4e4d0136efc8.1731671441.git.lorenzo.stoakes@oracle.com/

Lorenzo Stoakes (4):
  mm: avoid unsafe VMA hook invocation when error arises on mmap hook
  mm: unconditionally close VMAs on error
  mm: refactor arch_calc_vm_flag_bits() and arm64 MTE handling
  mm: resolve faulty mmap_region() error path behaviour

 arch/arm64/include/asm/mman.h |  10 ++-
 include/linux/mman.h          |   7 +-
 mm/internal.h                 |  19 ++++++
 mm/mmap.c                     | 120 ++++++++++++++++++----------------
 mm/nommu.c                    |   9 ++-
 mm/shmem.c                    |   3 -
 mm/util.c                     |  33 ++++++++++
 7 files changed, 130 insertions(+), 71 deletions(-)

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2.47.0