linux-kernel - [ 62/82] ext4: disallow hard-linked directory in ext4

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Message-Id: <20120607040345.410323140@linuxfoundation.org>
Date:	Thu, 07 Jun 2012 13:04:38 +0900
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Andreas Dilger <adilger@...ger.ca>,
	"Theodore Tso" <tytso@....edu>
Subject: [ 62/82] ext4: disallow hard-linked directory in ext4_lookup

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andreas Dilger <adilger@...ger.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@...ger.ca>
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/ext4/namei.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1037,6 +1037,12 @@ static struct dentry *ext4_lookup(struct
 			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,


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