Re: [PATCH] mm: page_alloc: validate buddy before check its migratetype.

Steven Rostedt
2022-03-30T22:29:26Z

On Wed, 30 Mar 2022 18:12:38 -0400
Zi Yan <zi.yan@sent.com> wrote:

> From: Zi Yan <ziy@nvidia.com>
>
> Whenever a buddy page is found, page_is_buddy() should be called to
> check its validity. Add the missing check during pageblock merge check.
>
> Fixes: 1dd214b8f21c ("mm: page_alloc: avoid merging non-fallbackable pageblocks with others")

Link: https://lore.kernel.org/all/20220330154208.71aca532@gandalf.local.home/

>
> Reported-by: Steven Rostedt <rostedt@goodmis.org>

Tested-by: Steven Rostedt (Google) <rostedt@goodmis.org>

-- Steve

> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
> mm/page_alloc.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index bdc8f60ae462..6c6af8658775 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1108,6 +1108,9 @@ static inline void __free_one_page(struct page *page,
>
> buddy_pfn = __find_buddy_pfn(pfn, order);
> buddy = page + (buddy_pfn - pfn);
> +
> + if (!page_is_buddy(page, buddy, order))
> + goto done_merging;
> buddy_mt = get_pageblock_migratetype(buddy);
>
> if (migratetype != buddy_mt