linux-kernel - [PATCH 5.11 236/775] f2fs: fix null page reference in redirty

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Message-Id: <20210301161213.291220418@linuxfoundation.org>
Date:   Mon,  1 Mar 2021 17:06:44 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Daeho Jeong <daehojeong@...gle.com>,
        Colin Ian King <colin.king@...onical.com>,
        Chao Yu <yuchao0@...wei.com>, Jaegeuk Kim <jaegeuk@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.11 236/775] f2fs: fix null page reference in redirty_blocks

From: Daeho Jeong <daehojeong@...gle.com>

[ Upstream commit df0736d70c4fa6ed711ba103b61880fe72bb4777 ]

By Colin's static analysis, we found out there is a null page reference
under low memory situation in redirty_blocks. I've made the page finding
loop stop immediately and return an error not to cause further memory
pressure when we run into a failure to find a page under low memory
condition.

Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
Reported-by: Colin Ian King <colin.king@...onical.com>
Fixes: 5fdb322ff2c2 ("f2fs: add F2FS_IOC_DECOMPRESS_FILE and F2FS_IOC_COMPRESS_FILE")
Reviewed-by: Colin Ian King <colin.king@...onical.com>
Reviewed-by: Chao Yu <yuchao0@...wei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/f2fs/file.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index f585545277d77..cd62b0d3369ab 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -4043,8 +4043,10 @@ static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len)
 
 	for (i = 0; i < page_len; i++, redirty_idx++) {
 		page = find_lock_page(mapping, redirty_idx);
-		if (!page)
-			ret = -ENOENT;
+		if (!page) {
+			ret = -ENOMEM;
+			break;
+		}
 		set_page_dirty(page);
 		f2fs_put_page(page, 1);
 		f2fs_put_page(page, 0);
-- 
2.27.0