cifs: always do is_path_accessible check in cifs_mount

BugLink: http://bugs.launchpad.net/bugs/769042

commit 70945643722ffeac779d2529a348f99567fa5c33 upstream.

Currently, we skip doing the is_path_accessible check in cifs_mount if
there is no prefixpath. I have a report of at least one server however
that allows a TREE_CONNECT to a share that has a DFS referral at its
root. The reporter in this case was using a UNC that had no prefixpath,
so the is_path_accessible check was not triggered and the box later hit
a BUG() because we were chasing a DFS referral on the root dentry for
the mount.

This patch fixes this by removing the check for a zero-length
prefixpath.  That should make the is_path_accessible check be done in
this situation and should allow the client to chase the DFS referral at
mount time instead.

Reported-and-Tested-by: Yogesh Sharma <ysharma@cymer.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Leann Ogasawara <leann.ogasawara@canonical.com>

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 8d6c17a..d3d836d 100644 (file)
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2826,7 +2826,7 @@ try_mount_again:
 
 remote_path_check:
        /* check if a whole path (including prepath) is not remote */
-       if (!rc && cifs_sb->prepathlen && tcon) {
+       if (!rc && tcon) {
                /* build_path_to_root works only when we have a valid tcon */
                full_path = cifs_build_path_to_root(cifs_sb, tcon);
                if (full_path == NULL) {