The patch titled
Subject: mm/huge_memory: check new folio order when split a folio
has been added to the -mm mm-unstable branch. Its filename is
mm-huge_memory-check-new-folio-order-when-split-a-folio.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-huge_memory-check-new-folio-order-when-split-a-folio.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Zi Yan <ziy@xxxxxxxxxx>
Subject: mm/huge_memory: check new folio order when split a folio
Date: Thu, 7 Mar 2024 13:18:53 -0500
A folio can only be split into lower orders. Check new_order to make sure
it is smaller than input folio order.
Link: https://lkml.kernel.org/r/20240307181854.138928-1-zi.yan@xxxxxxxx
Fixes: c010d47f107f ("mm: thp: split huge page to any lower order pages")
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Closes: https://lore.kernel.org/linux-mm/7dda9283-b437-4cf8-ab0d-83c330deb9c0@moroto.mountain/
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 3 +++
1 file changed, 3 insertions(+)
--- a/mm/huge_memory.c~mm-huge_memory-check-new-folio-order-when-split-a-folio
+++ a/mm/huge_memory.c
@@ -3052,6 +3052,9 @@ int split_huge_page_to_list_to_order(str
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");
_
Patches currently in -mm which might be from ziy@xxxxxxxxxx are
mm-huge_memory-check-new-folio-order-when-split-a-folio.patch
mm-huge_memory-skip-invalid-debugfs-new_order-input-for-folio-split.patch
