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From: Zi Yan <zi.yan@sent.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org
Cc: Zi Yan <ziy@nvidia.com>,
	Dan Carpenter <dan.carpenter@linaro.org>,
	"Pankaj Raghav (Samsung)" <kernel@pankajraghav.com>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	David Hildenbrand <david@redhat.com>,
	Yang Shi <shy828301@gmail.com>,
	Yu Zhao <yuzhao@google.com>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Ryan Roberts <ryan.roberts@arm.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH 1/2] mm/huge_memory: check new folio order when split a folio
Date: Thu,  7 Mar 2024 13:18:53 -0500
Message-ID: <20240307181854.138928-1-zi.yan@sent.com>
Reply-To: Zi Yan <ziy@nvidia.com>
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From: Zi Yan <ziy@nvidia.com>

A folio can only be split into lower orders. Check new_order to make sure
it is smaller than input folio order.

Link: https://lore.kernel.org/linux-mm/7dda9283-b437-4cf8-ab0d-83c330deb9c0@moroto.mountain/
Fixes: c010d47f107f ("mm: thp: split huge page to any lower order pages")
Signed-off-by: Zi Yan <ziy@nvidia.com>
---
 mm/huge_memory.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a81a09236c16..57fca7bffd20 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3052,6 +3052,9 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
 	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 	VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
 
+	if (new_order >= folio_order(folio))
+		return -EINVAL;
+
 	/* Cannot split anonymous THP to order-1 */
 	if (new_order == 1 && folio_test_anon(folio)) {
 		VM_WARN_ONCE(1, "Cannot split to order-1 folio");
-- 
2.43.0