linux-kernel - [PATCH 3.13 103/140] vfs: Is mounted should be testing mnt

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Message-Id: <20140204211039.914893806@linuxfoundation.org>
Date:	Tue,  4 Feb 2014 13:11:30 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 3.13 103/140] vfs: Is mounted should be testing mnt_ns for NULL or error.

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

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

From: "Eric W. Biederman" <ebiederm@...ssion.com>

commit 260a459d2e39761fbd39803497205ce1690bc7b1 upstream.

A bug was introduced with the is_mounted helper function in
commit f7a99c5b7c8bd3d3f533c8b38274e33f3da9096e
Author: Al Viro <viro@...iv.linux.org.uk>
Date:   Sat Jun 9 00:59:08 2012 -0400

    get rid of ->mnt_longterm

    it's enough to set ->mnt_ns of internal vfsmounts to something
    distinct from all struct mnt_namespace out there; then we can
    just use the check for ->mnt_ns != NULL in the fast path of
    mntput_no_expire()

    Signed-off-by: Al Viro <viro@...iv.linux.org.uk>

The intent was to test if the real_mount(vfsmount)->mnt_ns was
NULL_OR_ERR but the code is actually testing real_mount(vfsmount)
and always returning true.

The result is d_absolute_path returning paths it should be hiding.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/mount.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/mount.h
+++ b/fs/mount.h
@@ -74,7 +74,7 @@ static inline int mnt_has_parent(struct
 static inline int is_mounted(struct vfsmount *mnt)
 {
 	/* neither detached nor internal? */
-	return !IS_ERR_OR_NULL(real_mount(mnt));
+	return !IS_ERR_OR_NULL(real_mount(mnt)->mnt_ns);
 }
 
 extern struct mount *__lookup_mnt(struct vfsmount *, struct dentry *);


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