On Wed 16-11-16 01:28:19, Kirill A. Shutemov wrote:
> 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.
Ok, so do you prefer me to keep this patch or discard it? Either is fine with
me. It was just a cleanup I wrote when factoring out the functionality.
Honza
>
> > ---
> > 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
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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