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    SubjectRe: [PATCH 2/2] hugepages: Fix use after free bug in "quota" handling
    On Thu, Feb 16, 2012 at 08:33:51PM +0800, Hillf Danton wrote:
    > On Thu, Feb 16, 2012 at 12:24 PM, David Gibson
    > <david@gibson.dropbear.id.au> wrote:
    > > @@ -1046,12 +1124,12 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
    > >        if (!page) {
    > >                page = alloc_buddy_huge_page(h, NUMA_NO_NODE);
    > >                if (!page) {
    > > -                       hugetlb_put_quota(inode->i_mapping, chg);
    > > +                       hugepage_subpool_put_pages(spool, chg);
    > >                        return ERR_PTR(-VM_FAULT_SIGBUS);
    > >                }
    > >        }
    > >
    > > -       set_page_private(page, (unsigned long) mapping);
    > > +       set_page_private(page, (unsigned long)spool);

    Sorry for the very delayed reply. Somehow I never spotted this when
    it first came. I think I must have acidentally deleted it when
    cleaning out automated messages and spam.

    > Page mapping is used in unmap_ref_private(), and I am
    > wondering it no longer works:-(

    Good point. But unmap_ref_private() does take the vma, so it should
    be able to get to the mapping from there. I'll respin doing that,
    instead of using page_private().

    > > @@ -2392,7 +2471,8 @@ retry_avoidcopy:
    > >
    > >        /* Drop page_table_lock as buddy allocator may be called */
    > >        spin_unlock(&mm->page_table_lock);
    > > -       new_page = alloc_huge_page(vma, address, outside_reserve);
    > > +       new_page = alloc_huge_page(vma, address, outside_reserve,
    > > +                                  subpool_vma(vma));
    >
    > Change in the number of parameters of alloc_huge_page()
    > looks unnecessary.

    Because alloc_huge_page() also takes vma. Yeah, fair enough. I'll
    change that in the respin too.

    --
    David Gibson | I'll have my music baroque, and my code
    david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
    | _way_ _around_!
    http://www.ozlabs.org/~dgibson
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