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From:   Zi Yan <zi.yan@sent.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>,
        Steven Rostedt <rostedt@goodmis.org>
Cc:     David Hildenbrand <david@redhat.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Mel Gorman <mgorman@techsingularity.net>,
        Mike Rapoport <rppt@kernel.org>,
        Oscar Salvador <osalvador@suse.de>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Zi Yan <ziy@nvidia.com>
Subject: [PATCH] mm: page_alloc: validate buddy before check its migratetype.
Date:   Wed, 30 Mar 2022 18:12:38 -0400
Message-Id: <20220330221238.396357-1-zi.yan@sent.com>
Reply-To: Zi Yan <ziy@nvidia.com>
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

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 pagebl=
ocks 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,
=20
 		buddy_pfn =3D __find_buddy_pfn(pfn, order);
 		buddy =3D page + (buddy_pfn - pfn);
+
+		if (!page_is_buddy(page, buddy, order))
+			goto done_merging;
 		buddy_mt =3D get_pageblock_migratetype(buddy);
=20
 		if (migratetype !=3D buddy_mt
--=20
2.35.1