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    Subject[RFC PATCH v4 24/27] mm/mmap: Create a guard area between VMAs
    Date
    Create a guard area between VMAs, to detect memory corruption.

    Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
    ---
    include/linux/mm.h | 30 ++++++++++++++++++++----------
    1 file changed, 20 insertions(+), 10 deletions(-)

    diff --git a/include/linux/mm.h b/include/linux/mm.h
    index c4cc07baccda..3a823bdae09d 100644
    --- a/include/linux/mm.h
    +++ b/include/linux/mm.h
    @@ -2443,24 +2443,34 @@ static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * m
    static inline unsigned long vm_start_gap(struct vm_area_struct *vma)
    {
    unsigned long vm_start = vma->vm_start;
    + unsigned long gap;
    +
    + if (vma->vm_flags & VM_GROWSDOWN)
    + gap = stack_guard_gap;
    + else
    + gap = PAGE_SIZE;
    +
    + vm_start -= gap;
    + if (vm_start > vma->vm_start)
    + vm_start = 0;

    - if (vma->vm_flags & VM_GROWSDOWN) {
    - vm_start -= stack_guard_gap;
    - if (vm_start > vma->vm_start)
    - vm_start = 0;
    - }
    return vm_start;
    }

    static inline unsigned long vm_end_gap(struct vm_area_struct *vma)
    {
    unsigned long vm_end = vma->vm_end;
    + unsigned long gap;
    +
    + if (vma->vm_flags & VM_GROWSUP)
    + gap = stack_guard_gap;
    + else
    + gap = PAGE_SIZE;
    +
    + vm_end += gap;
    + if (vm_end < vma->vm_end)
    + vm_end = -PAGE_SIZE;

    - if (vma->vm_flags & VM_GROWSUP) {
    - vm_end += stack_guard_gap;
    - if (vm_end < vma->vm_end)
    - vm_end = -PAGE_SIZE;
    - }
    return vm_end;
    }

    --
    2.17.1
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