[ 38/82] ext4: disallow hard-linked directory in ext4_lookup

Ben Hutchings
2012-06-08T05:18:19Z

From: Andreas Dilger <adilger@dilger.ca>

commit 7e936b737211e6b54e34b71a827e56b872e958d8 upstream.

A hard-linked directory to its parent can cause the VFS to deadlock,
and is a sign of a corrupted file system. So detect this case in
ext4_lookup(), before the rmdir() lockup scenario can take place.

Signed-off-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/ext4/namei.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index a9fd5f4..daf8260 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1330,6 +1330,12 @@ static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, stru
EXT4_ERROR_INODE(dir, "bad inode number: %u", ino);
return ERR_PTR(-EIO);
}
+ if (unlikely(ino == dir->i_ino)) {
+ EXT4_ERROR_INODE(dir, "'%.*s' linked to parent dir",
+ dentry->d_name.len,
+ dentry->d_name.name);
+ return ERR_PTR(-EIO);
+ }
inode = ext4_iget(dir->i_sb, ino);
if (inode == ERR_PTR(-ESTALE)) {
EXT4_ERROR_INODE(dir,