apparmor: Fix case where long path names are failing due to disconnected path

BugLink: http://bugs.launchpad.net/bugs/955892

All failures from __d_path where being treated as disconnected paths,
however __d_path can also fail when the generated pathname is too long.

The initial ENAMETOOLONG error was being lost, and ENAMETOOLONG was only
returned if the subsequent dentry_path call resulted in that error.  Other
wise if the path was split across a mount point such that the dentry_path
fit within the buffer when the __d_path did not the failure was treated
as a disconnected path.

Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/path.c

diff --git a/security/apparmor/path.c b/security/apparmor/path.c
index 2daeea4..e91ffee 100644
--- a/security/apparmor/path.c
+++ b/security/apparmor/path.c
@@ -94,6 +94,8 @@
 	 * be returned.
 	 */
 	if (!res || IS_ERR(res)) {
+		if (PTR_ERR(res) == -ENAMETOOLONG)
+			return -ENAMETOOLONG;
 		connected = 0;
 		res = dentry_path_raw(path->dentry, buf, buflen);
 		if (IS_ERR(res)) {