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ocfs2: check existence of old dentry in ocfs2_link()

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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>
This commit is contained in:
Xue jiufei 2014-02-10 14:25:54 -08:00 committed by Linus Torvalds
parent c7d2cbc364
commit 0e048316ff
1 changed files with 17 additions and 0 deletions
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17
fs/ocfs2/namei.c
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@ -664,6 +664,7 @@ static int ocfs2_link(struct dentry *old_dentry,
struct ocfs2_super *osb = OCFS2_SB(dir->i_sb);
struct ocfs2_dir_lookup_result lookup = { NULL, };
sigset_t oldset;
u64 old_de_ino;
trace_ocfs2_link((unsigned long long)OCFS2_I(inode)->ip_blkno,
old_dentry->d_name.len, old_dentry->d_name.name,
@ -686,6 +687,22 @@ static int ocfs2_link(struct dentry *old_dentry,
goto out;
}
err = ocfs2_lookup_ino_from_name(dir, old_dentry->d_name.name,
old_dentry->d_name.len, &old_de_ino);
if (err) {
err = -ENOENT;
goto out;
}
/*
* Check whether another node removed the source inode while we
* were in the vfs.
*/
if (old_de_ino != OCFS2_I(inode)->ip_blkno) {
err = -ENOENT;
goto out;
}
err = ocfs2_check_dir_for_entry(dir, dentry->d_name.name,
dentry->d_name.len);
if (err)