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

Zi Yan
2022-03-30T22:12:58Z

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")

Reported-by: Steven Rostedt <rostedt@goodmis.org>
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
--
2.35.1