linux-kernel - Re: [PATCH 2/2] hugepages: Fix use after free bug in "quota" handling

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Date:	Thu, 16 Feb 2012 20:33:51 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	David Gibson <david@...son.dropbear.id.au>
Cc:	akpm@...ux-foundation.org, abarry@...y.com, hughd@...gle.com,
	mgorman@...e.de, minchan.kim@...il.com, paulus@...ba.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] hugepages: Fix use after free bug in "quota" handling

On Thu, Feb 16, 2012 at 12:24 PM, David Gibson
<david@...son.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);
>

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

> @@ -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.
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