From: Vasily Averin <vvs@parallels.com>
Date: Mon, 21 Jul 2014 08:30:23 +0000 (+0400)
Subject: fs: umount on symlink leaks mnt count
X-Git-Tag: firefly_0821_release~176^2~3549^2
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=295dc39d941dc2ae53d5c170365af4c9d5c16212;p=firefly-linux-kernel-4.4.55.git

fs: umount on symlink leaks mnt count

Currently umount on symlink blocks following umount:

/vz is separate mount

# ls /vz/ -al | grep test
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 -l /vz/testlink
umount: /vz/testlink: not mounted (expected)

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

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

Signed-off-by: Vasily Averin <vvs@openvz.org>
Acked-by: Ian Kent <raven@themaw.net>
Acked-by: Jeff Layton <jlayton@primarydata.com>
Cc: stable@vger.kernel.org
Signed-off-by: Christoph Hellwig <hch@lst.de>
---

diff --git a/fs/namei.c b/fs/namei.c
index 985c6f368485..9eb787e5c167 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2256,9 +2256,10 @@ done:
 		goto out;
 	}
 	path->dentry = dentry;
-	path->mnt = mntget(nd->path.mnt);
+	path->mnt = nd->path.mnt;
 	if (should_follow_link(dentry, nd->flags & LOOKUP_FOLLOW))
 		return 1;
+	mntget(path->mnt);
 	follow_mount(path);
 	error = 0;
 out: