linux-kernel - [PATCH v2] mm/page_alloc.c: avoid accessing uninitialized pcp page migratetype

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Date:   Thu, 2 Sep 2021 19:54:47 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <vbabka@...e.cz>, <peterz@...radead.org>,
        <mgorman@...hsingularity.net>, <david@...hat.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH v2] mm/page_alloc.c: avoid accessing uninitialized pcp page migratetype

If it's not prepared to free unref page, the pcp page migratetype is
unset. Thus We will get rubbish from get_pcppage_migratetype() and
might list_del &page->lru again after it's already deleted from the
list leading to grumble about data corruption.

Fixes: df1acc856923 ("mm/page_alloc: avoid conflating IRQs disabled with zone->lock")
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
Acked-by: Mel Gorman <mgorman@...hsingularity.net>
Cc: <stable@...r.kernel.org>
---
 mm/page_alloc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9c09dcb24149..a3c6acafa478 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3420,8 +3420,10 @@ void free_unref_page_list(struct list_head *list)
 	/* Prepare pages for freeing */
 	list_for_each_entry_safe(page, next, list, lru) {
 		pfn = page_to_pfn(page);
-		if (!free_unref_page_prepare(page, pfn, 0))
+		if (!free_unref_page_prepare(page, pfn, 0)) {
 			list_del(&page->lru);
+			continue;
+		}
 
 		/*
 		 * Free isolated pages directly to the allocator, see
-- 
2.23.0