linux-kernel - [PATCH] mm/folio-compact: fix potential NULL pointer in pagecache_get

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Message-ID: <20220727064621.534528-1-liuyongqiang13@huawei.com>
Date:   Wed, 27 Jul 2022 06:46:21 +0000
From:   Yongqiang Liu <liuyongqiang13@...wei.com>
To:     <willy@...radead.org>, <dhowells@...hat.com>,
        <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
CC:     <zhangxiaoxu5@...wei.com>, <liuyongqiang13@...wei.com>,
        <yanaijie@...wei.com>, <vbabka@...e.cz>,
        <wangkefeng.wang@...wei.com>
Subject: [PATCH] mm/folio-compact: fix potential NULL pointer in pagecache_get_page

When __filemap_get_folio() failed and returned NULL, we would
get a NULL pointer dereference in pagecache_get_page.

Fixes: 3f0c6a07fee6 ("mm/filemap: Add filemap_get_folio")
Signed-off-by: Yongqiang Liu <liuyongqiang13@...wei.com>
Cc: <stable@...r.kernel.org> # 5.16
---
 mm/folio-compat.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index 20bc15b57d93..7b21393480e0 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -124,7 +124,9 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
 	struct folio *folio;
 
 	folio = __filemap_get_folio(mapping, index, fgp_flags, gfp);
-	if ((fgp_flags & FGP_HEAD) || !folio || xa_is_value(folio))
+	if (!folio)
+		return NULL;
+	if ((fgp_flags & FGP_HEAD) || xa_is_value(folio))
 		return &folio->page;
 	return folio_file_page(folio, index);
 }
-- 
2.25.1