[3.11.y.z extended stable] Patch "fs: umount on symlink leaks mnt count" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    fs: umount on symlink leaks mnt count

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 7e88f8ace02e1830016c83d6c86cabd11cec9510 Mon Sep 17 00:00:00 2001
From: Vasily Averin <vvs at parallels.com>
Date: Mon, 21 Jul 2014 12:30:23 +0400
Subject: fs: umount on symlink leaks mnt count

commit 295dc39d941dc2ae53d5c170365af4c9d5c16212 upstream.

Currently umount on symlink blocks following umount:

/vz is separate mount

drwxr-xr-x.  2 root root       4096 Jul 19 01:14 testdir
lrwxrwxrwx.  1 root root         11 Jul 19 01:16 testlink -> /vz/testdir
umount: /vz/testlink: not mounted (expected)

umount: /vz: device is busy. (unexpected)

In this case mountpoint_last() gets an extra refcount on path->mnt

Signed-off-by: Vasily Averin <vvs at openvz.org>
Acked-by: Ian Kent <raven at themaw.net>
Acked-by: Jeff Layton <jlayton at primarydata.com>
Signed-off-by: Christoph Hellwig <hch at lst.de>
Cc: Neil Brown <neilb at suse.de>
[ luis: backported to 3.11: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/namei.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/namei.c b/fs/namei.c
index a10bd2f8b66b..2d36c4651627 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2260,10 +2260,11 @@ error_check:
 			dput(dentry);
 		} else {
 			path->dentry = dentry;
-			path->mnt = mntget(nd->path.mnt);
+			path->mnt = nd->path.mnt;
 			if (should_follow_link(dentry->d_inode,
 						nd->flags & LOOKUP_FOLLOW))
 				return 1;
+			mntget(path->mnt);
 			follow_mount(path);
 		}
 	}
--
1.9.1