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| author | Suren Baghdasaryan <surenb@google.com> | 2023-07-08 21:12:11 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2023-07-08 23:08:02 +0200 |
| commit | 33313a747e81af9f31d0d45de78c9397fa3655eb (patch) | |
| tree | 9e4050107b487128f0b628c7b7117082953e23eb /mm/mmap.c | |
| parent | mm: lock a vma before stack expansion (diff) | |
| download | linux-33313a747e81af9f31d0d45de78c9397fa3655eb.tar.xz linux-33313a747e81af9f31d0d45de78c9397fa3655eb.zip | |
mm: lock newly mapped VMA which can be modified after it becomes visible
mmap_region adds a newly created VMA into VMA tree and might modify it
afterwards before dropping the mmap_lock. This poses a problem for page
faults handled under per-VMA locks because they don't take the mmap_lock
and can stumble on this VMA while it's still being modified. Currently
this does not pose a problem since post-addition modifications are done
only for file-backed VMAs, which are not handled under per-VMA lock.
However, once support for handling file-backed page faults with per-VMA
locks is added, this will become a race.
Fix this by write-locking the VMA before inserting it into the VMA tree.
Other places where a new VMA is added into VMA tree do not modify it
after the insertion, so do not need the same locking.
Cc: stable@vger.kernel.org
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to '')
| -rw-r--r-- | mm/mmap.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index c66e4622a557..84c71431a527 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2812,6 +2812,8 @@ cannot_expand: if (vma->vm_file) i_mmap_lock_write(vma->vm_file->f_mapping); + /* Lock the VMA since it is modified after insertion into VMA tree */ + vma_start_write(vma); vma_iter_store(&vmi, vma); mm->map_count++; if (vma->vm_file) { |