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

Message

Lorenzo Stoakes Nov. 15, 2024, 12:40 p.m. UTC

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.

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                     | 119 ++++++++++++++++++----------------
 mm/nommu.c                    |   9 ++-
 mm/shmem.c                    |   3 -
 mm/util.c                     |  33 ++++++++++
 7 files changed, 129 insertions(+), 71 deletions(-)

--
2.47.0

Comments

Vlastimil Babka Nov. 15, 2024, 7:11 p.m. UTC | #1

On 11/15/24 13:40, Lorenzo Stoakes wrote:
> 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().

Seems adding 9a9d0b829901 ("mm: move dummy_vm_ops out of a header") as
prerequisity would have been less work, but I didn't find a bug in your
adjustments so seems fine to me.

> 
> * 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.
> 
> 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

Aside from the suspected memory leak I reported for 4/4,

Reviewed-by: Vlastimil Babka <[e-mail]>

>  arch/arm64/include/asm/mman.h |  10 ++-
>  include/linux/mman.h          |   7 +-
>  mm/internal.h                 |  19 ++++++
>  mm/mmap.c                     | 119 ++++++++++++++++++----------------
>  mm/nommu.c                    |   9 ++-
>  mm/shmem.c                    |   3 -
>  mm/util.c                     |  33 ++++++++++
>  7 files changed, 129 insertions(+), 71 deletions(-)
> 
> --
> 2.47.0

Liam R. Howlett Nov. 15, 2024, 8:09 p.m. UTC | #2

* Lorenzo Stoakes <[e-mail]> [241115 07:40]:
> 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.
> 

Besides that one line fix (thanks Vlastimil!), these look good.

Reviewed-by: Liam R. Howlett <[e-mail]>

> 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                     | 119 ++++++++++++++++++----------------
>  mm/nommu.c                    |   9 ++-
>  mm/shmem.c                    |   3 -
>  mm/util.c                     |  33 ++++++++++
>  7 files changed, 129 insertions(+), 71 deletions(-)
> 
> --
> 2.47.0