On Fri, Nov 04, 2016 at 05:25:07AM +0100, Jan Kara wrote:
> We don't check whether vma->vm_ops is NULL in do_shared_fault() so
> there's hardly any point in checking it in wp_page_shared() or
> wp_pfn_shared() which get called only for shared file mappings as well.
>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
Well, I'm not sure about this.
do_shared_fault() doesn't have the check since we checked it upper by
stack: see vma_is_anonymous() in handle_pte_fault().
In principal, it should be fine. But random crappy driver has potential to
blow it up.
> ---
> mm/memory.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 7be96a43d5ac..26b2858e6a12 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2275,7 +2275,7 @@ static int wp_pfn_shared(struct vm_fault *vmf)
> {
> struct vm_area_struct *vma = vmf->vma;
>
> - if (vma->vm_ops && vma->vm_ops->pfn_mkwrite) {
> + if (vma->vm_ops->pfn_mkwrite) {
> int ret;
>
> pte_unmap_unlock(vmf->pte, vmf->ptl);
> @@ -2305,7 +2305,7 @@ static int wp_page_shared(struct vm_fault *vmf, struct page *old_page)
>
> get_page(old_page);
>
> - if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
> + if (vma->vm_ops->page_mkwrite) {
> int tmp;
>
> pte_unmap_unlock(vmf->pte, vmf->ptl);
> --
> 2.6.6
>
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--
Kirill A. Shutemov
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