linux-kernel - [PATCH 4/4] mm/memory-failure.c: fix potential VM_BUG_ON_PAGE in split_huge_page_to

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Date:   Mon, 28 Feb 2022 22:02:45 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>, <naoya.horiguchi@....com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH 4/4] mm/memory-failure.c: fix potential VM_BUG_ON_PAGE in split_huge_page_to_list

The huge zero page could reach here and if we ever try to split it, the
VM_BUG_ON_PAGE will be triggered in split_huge_page_to_list(). Also the
non-lru compound movable pages could be taken for transhuge pages. Skip
these pages by checking PageLRU because huge zero page isn't lru page as
non-lru compound movable pages.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/memory-failure.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 23bfd809dc8c..ac6492e36978 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1792,6 +1792,20 @@ int memory_failure(unsigned long pfn, int flags)
 	}
 
 	if (PageTransHuge(hpage)) {
+		/*
+		 * The non-lru compound movable pages could be taken for
+		 * transhuge pages. Also huge zero page could reach here
+		 * and if we ever try to split it, the VM_BUG_ON_PAGE will
+		 * be triggered in split_huge_page_to_list(). Skip these
+		 * pages by checking PageLRU because huge zero page isn't
+		 * lru page as non-lru compound movable pages.
+		 */
+		if (!PageLRU(hpage)) {
+			put_page(p);
+			action_result(pfn, MF_MSG_UNSPLIT_THP, MF_IGNORED);
+			res = -EBUSY;
+			goto unlock_mutex;
+		}
 		/*
 		 * The flag must be set after the refcount is bumped
 		 * otherwise it may race with THP split.
-- 
2.23.0