ecryptfs: release reference to lower mount if interpose fails

In ecryptfs_lookup_and_interpose_lower() the lower mount is not decremented
if allocation of a dentry info struct failed. As a result the lower filesystem
cant be unmounted any more (since it is considered busy). This patch corrects
the reference counting.
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Cc: stable@kernel.org
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

fs/ecryptfs/inode.c

@@ -264,7 +264,7 @@ int ecryptfs_lookup_and_interpose_lower(struct dentry *ecryptfs_dentry,
 		printk(KERN_ERR "%s: Out of memory whilst attempting "
 		       "to allocate ecryptfs_dentry_info struct\n",
 			__func__);
-		goto out_dput;
+		goto out_put;
 	}
 	ecryptfs_set_dentry_lower(ecryptfs_dentry, lower_dentry);
 	ecryptfs_set_dentry_lower_mnt(ecryptfs_dentry, lower_mnt);
@@ -339,8 +339,9 @@ int ecryptfs_lookup_and_interpose_lower(struct dentry *ecryptfs_dentry,
 out_free_kmem:
 	kmem_cache_free(ecryptfs_header_cache_2, page_virt);
 	goto out;
-out_dput:
+out_put:
 	dput(lower_dentry);
+	mntput(lower_mnt);
 	d_drop(ecryptfs_dentry);
 out:
 	return rc;