Re: [PATCH 5.10.y 0/4] fix error handling in mmap_region() and refactor (hotfixes)

[Vlastimil Babka <vbabka@suse.cz>]

On 11/15/24 13:36, Lorenzo Stoakes wrote:
> Critical fixes for mmap_region(), backported to 5.10.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.
> 
> * In 5.10 we must handle VM_DENYWRITE. Since this is done at the top of the
>   file-backed VMA handling logic, and importantly before mmap_file() invocation,
>   this does not imply any additional difficult error handling on partial
>   completion of mapping so has no significant impact.

Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

> 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                     | 82 +++++++++++++++++++++--------------
>  mm/nommu.c                    |  9 ++--
>  mm/shmem.c                    |  3 --
>  mm/util.c                     | 33 ++++++++++++++
>  7 files changed, 117 insertions(+), 46 deletions(-)
> 
> --
> 2.47.0