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    Subject[PATCH v2 6/7] mm: Introduce find_vma_filter_flags() helper
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    Date
    This patch introduce a new helper, which returns
    vma of enough length at given address, but only
    if it does not contain passed flags.

    v2: New

    Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
    ---
    include/linux/mm.h | 3 +++
    mm/mremap.c | 39 ++++++++++++++++++++++++++-------------
    2 files changed, 29 insertions(+), 13 deletions(-)

    diff --git a/include/linux/mm.h b/include/linux/mm.h
    index 54328d08dbdd..65ceb56acd44 100644
    --- a/include/linux/mm.h
    +++ b/include/linux/mm.h
    @@ -1515,6 +1515,9 @@ void unmap_mapping_pages(struct address_space *mapping,
    pgoff_t start, pgoff_t nr, bool even_cows);
    void unmap_mapping_range(struct address_space *mapping,
    loff_t const holebegin, loff_t const holelen, int even_cows);
    +struct vm_area_struct *find_vma_without_flags(struct mm_struct *mm,
    + unsigned long addr, unsigned long len,
    + unsigned long prohibited_flags);
    #else
    static inline vm_fault_t handle_mm_fault(struct vm_area_struct *vma,
    unsigned long address, unsigned int flags)
    diff --git a/mm/mremap.c b/mm/mremap.c
    index 9a96cfc28675..dabae6a70287 100644
    --- a/mm/mremap.c
    +++ b/mm/mremap.c
    @@ -430,14 +430,37 @@ static unsigned long move_vma(struct vm_area_struct *vma,
    return new_addr;
    }

    +struct vm_area_struct *find_vma_without_flags(struct mm_struct *mm,
    + unsigned long addr, unsigned long len,
    + unsigned long prohibited_flags)
    +{
    + struct vm_area_struct *vma = find_vma(mm, addr);
    +
    + if (!vma || vma->vm_start > addr)
    + return ERR_PTR(-EFAULT);
    +
    + /* vm area boundaries crossing */
    + if (len > vma->vm_end - addr)
    + return ERR_PTR(-EFAULT);
    +
    + if (vma->vm_flags & prohibited_flags)
    + return ERR_PTR(-EFAULT);
    +
    + return vma;
    +}
    +
    static struct vm_area_struct *vma_to_resize(unsigned long addr,
    unsigned long old_len, unsigned long new_len, unsigned long *p)
    {
    struct mm_struct *mm = current->mm;
    - struct vm_area_struct *vma = find_vma(mm, addr);
    - unsigned long pgoff;
    + struct vm_area_struct *vma;
    + unsigned long pgoff, prohibited_flags = VM_HUGETLB;

    - if (!vma || vma->vm_start > addr)
    + if (old_len != new_len)
    + prohibited_flags |= VM_DONTEXPAND | VM_PFNMAP;
    +
    + vma = find_vma_without_flags(mm, addr, old_len, prohibited_flags);
    + if (IS_ERR(vma))
    return ERR_PTR(-EFAULT);

    /*
    @@ -453,13 +476,6 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
    return ERR_PTR(-EINVAL);
    }

    - if (is_vm_hugetlb_page(vma))
    - return ERR_PTR(-EINVAL);
    -
    - /* We can't remap across vm area boundaries */
    - if (old_len > vma->vm_end - addr)
    - return ERR_PTR(-EFAULT);
    -
    if (new_len == old_len)
    return vma;

    @@ -469,9 +485,6 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
    if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
    return ERR_PTR(-EINVAL);

    - if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
    - return ERR_PTR(-EFAULT);
    -
    if (vma->vm_flags & VM_LOCKED) {
    unsigned long locked, lock_limit;
    locked = atomic64_read(&mm->locked_vm) << PAGE_SHIFT;
    \
     
     \ /
      Last update: 2019-05-20 16:02    [W:3.003 / U:0.412 seconds]
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