linux-kernel - [PATCH 3.11 115/137] fs: umount on symlink leaks mnt count

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Date:	Mon, 18 Aug 2014 10:32:56 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Vasily Averin <vvs@...nvz.org>, Christoph Hellwig <hch@....de>,
	Neil Brown <neilb@...e.de>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.11 115/137] fs: umount on symlink leaks mnt count

3.11.10.15 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vasily Averin <vvs@...allels.com>

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@...nvz.org>
Acked-by: Ian Kent <raven@...maw.net>
Acked-by: Jeff Layton <jlayton@...marydata.com>
Signed-off-by: Christoph Hellwig <hch@....de>
Cc: Neil Brown <neilb@...e.de>
[ luis: backported to 3.11: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@...onical.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

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