f2fs: check name_len of dir entry to prevent from deadloop

We assume that modification of some special application could result in zeroed
name_len, or it is consciously made by somebody. We will deadloop in
find_in_block when name_len of dir entry is zero.

This patch is added for preventing deadloop in above scenario.

change log from v1:
 o use f2fs_bug_on rather than break out from searching dir entry suggested by
Jaegeuk Kim.

Jaegeuk describe:
"Well, IMO, it would be good to add f2fs_bug_on() here with a specific comment.
In the current phase of f2fs, it is more important to investigate the file
system bugs, rather than workarounds for any corrupted images.
And, definitely it needs to stop the kernel if any corrupted image was mounted,
so that we can figure out where the bugs are occurred."

Suggested-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index e84e8807c6514fa92a7912ea6986a5e767daacea..bcf893c3d9036d0eb743ff8c34bae2eda23e9582 100644 (file)
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -121,6 +121,13 @@ static struct f2fs_dir_entry *find_in_block(struct page *dentry_page,
                        *max_slots = max_len;
                        max_len = 0;
                }
+
+               /*
+                * For the most part, it should be a bug when name_len is zero.
+                * We stop here for figuring out where the bugs are occurred.
+                */
+               f2fs_bug_on(!de->name_len);
+
                bit_pos += GET_DENTRY_SLOTS(le16_to_cpu(de->name_len));
        }