Thanks for the updates!
Best wishes,
--
Ning Qu (曲宁) | Software Engineer | quning@xxxxxxxxxx | +1-408-418-6066
On Mon, Mar 3, 2014 at 3:07 AM, Kirill A. Shutemov
<kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
> Ning Qu wrote:
>> Btw, should we first check if page returned by radix_tree_deref_slot is NULL?
>
> Yes, we should. I don't know how I missed that. :(
>
> The patch below should address both issues.
>
> From dca24c9a1f31ee1599fe81e9a60d4f87a4eaf0ea Mon Sep 17 00:00:00 2001
> From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> Date: Mon, 3 Mar 2014 12:07:03 +0200
> Subject: [PATCH] mm: filemap_map_pages() avoid dereference NULL/exception
> slots
>
> radix_tree_deref_slot() can return NULL: add missed check.
>
> Do no dereference 'page': we can get there as result of
> radix_tree_exception(page) check.
>
> Reported-by: Hugh Dickins <hughd@xxxxxxxxxx>
> Reported-by: Ning Qu <quning@xxxxxxxxxx>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> ---
> mm/filemap.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 5f4fe7f0c258..e48624634927 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1745,6 +1745,8 @@ void filemap_map_pages(struct vm_area_struct *vma, struct vm_fault *vmf)
> break;
> repeat:
> page = radix_tree_deref_slot(slot);
> + if (unlikely(!page))
> + goto next;
> if (radix_tree_exception(page)) {
> if (radix_tree_deref_retry(page))
> break;
> @@ -1790,7 +1792,7 @@ unlock:
> skip:
> page_cache_release(page);
> next:
> - if (page->index == vmf->max_pgoff)
> + if (iter.index == vmf->max_pgoff)
> break;
> }
> rcu_read_unlock();
> --
> Kirill A. Shutemov
>
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