Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull namespace fix from Eric Biederman:
 "Benjamin Coddington noticed an unkillable busy loop in the kernel that
  anyone who is sufficiently motivated can trigger. This bug did not
  exist in earlier kernels making this bug a regression.

  I have tested the change personally and confirmed that the bug exists
  and that the fix works. This fix has been picked up by linux-next and
  hopefully the automated testing bots and no problems have been
  reported from those sources.

  Ordinarily I would let something like this sit a little longer but I
  am going to be away at Linux Plumbers the rest of this week and I am
  afraid if I don't send the pull request now this fix will get lost"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  mnt: fix __detach_mounts infinite loop

fs/namespace.c

@@ -695,9 +695,6 @@ static struct mountpoint *lookup_mountpoint(struct dentry *dentry)
 
 	hlist_for_each_entry(mp, chain, m_hash) {
 		if (mp->m_dentry == dentry) {
-			/* might be worth a WARN_ON() */
-			if (d_unlinked(dentry))
-				return ERR_PTR(-ENOENT);
 			mp->m_count++;
 			return mp;
 		}
@@ -711,6 +708,9 @@ static struct mountpoint *get_mountpoint(struct dentry *dentry)
 	int ret;
 
 	if (d_mountpoint(dentry)) {
+		/* might be worth a WARN_ON() */
+		if (d_unlinked(dentry))
+			return ERR_PTR(-ENOENT);
 mountpoint:
 		read_seqlock_excl(&mount_lock);
 		mp = lookup_mountpoint(dentry);