linux-kernel - [PATCH] f2fs: fix to avoid out-of-boundary access in devs.path

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Message-ID: <20250711071450.207302-1-chao@kernel.org>
Date: Fri, 11 Jul 2025 15:14:50 +0800
From: Chao Yu <chao@...nel.org>
To: jaegeuk@...nel.org
Cc: linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org,
	Chao Yu <chao@...nel.org>
Subject: [PATCH] f2fs: fix to avoid out-of-boundary access in devs.path

- touch /mnt/f2fs/012345678901234567890123456789012345678901234567890123
- truncate -s $((1024*1024*1024)) \
  /mnt/f2fs/012345678901234567890123456789012345678901234567890123
- touch /mnt/f2fs/file
- truncate -s $((1024*1024*1024)) /mnt/f2fs/file
- mkfs.f2fs /mnt/f2fs/012345678901234567890123456789012345678901234567890123 \
  -c /mnt/f2fs/file
- mount /mnt/f2fs/012345678901234567890123456789012345678901234567890123 \
  /mnt/f2fs/loop

[16937.192225] F2FS-fs (loop0): Mount Device [ 0]: /mnt/f2fs/012345678901234567890123456789012345678901234567890123\xff\x01,      511,        0 -    3ffff
[16937.192268] F2FS-fs (loop0): Failed to find devices

If device path length equals to MAX_PATH_LEN, sbi->devs.path[] may
not end up w/ null character due to path array is fully filled, So
accidently, fields locate after path[] may be treated as part of
device path, result in parsing wrong device path.

struct f2fs_dev_info {
...
	char path[MAX_PATH_LEN];
...
};

Let's add one byte space for sbi->devs.path[] to store null
character of device path string.

Fixes: 3c62be17d4f5 ("f2fs: support multiple devices")
Signed-off-by: Chao Yu <chao@...nel.org>
---
 fs/f2fs/f2fs.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 8cded45cfbc7..64996153e4c8 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1289,7 +1289,7 @@ struct f2fs_bio_info {
 struct f2fs_dev_info {
 	struct file *bdev_file;
 	struct block_device *bdev;
-	char path[MAX_PATH_LEN];
+	char path[MAX_PATH_LEN + 1];
 	unsigned int total_segments;
 	block_t start_blk;
 	block_t end_blk;
-- 
2.49.0