ocfs2: check existence of old dentry in ocfs2_link()
authorXue jiufei <xuejiufei@huawei.com>
Mon, 10 Feb 2014 22:25:54 +0000 (14:25 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 11 Feb 2014 00:01:43 +0000 (16:01 -0800)
commit0e048316ff577e12c748e2d0a2e4f0f7b006654d
treef37ad130de45bf55b3cb43fcb8e5e06a924a41d8
parentc7d2cbc364b2a237b0ed1bdd7cbf8a24c8a89dfd
ocfs2: check existence of old dentry in ocfs2_link()

System call linkat first calls user_path_at(), check the existence of
old dentry, and then calls vfs_link()->ocfs2_link() to do the actual
work.  There may exist a race when Node A create a hard link for file
while node B rm it.

         Node A                          Node B
user_path_at()
  ->ocfs2_lookup(),
find old dentry exist
                                rm file, add inode say inodeA
                                to orphan_dir

call ocfs2_link(),create a
hard link for inodeA.

                                rm the link, add inodeA to orphan_dir
                                again

When orphan_scan work start, it calls ocfs2_queue_orphans() to do the
main work.  It first tranverses entrys in orphan_dir, linking all inodes
in this orphan_dir to a list look like this:

inodeA->inodeB->...->inodeA

When tranvering this list, it will fall into loop, calling iput() again
and again.  And finally trigger BUG_ON(inode->i_state & I_CLEAR).

Signed-off-by: joyce <xuejiufei@huawei.com>
Reviewed-by: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/ocfs2/namei.c