CIFS: Fix memory over bound bug in cifs_parse_mount_options

CIFS: Fix memory over bound bug in cifs_parse_mount_options

BugLink: http://bugs.launchpad.net/bugs/788691

commit 4906e50b37e6f6c264e7ee4237343eb2b7f8d16d upstream.

While password processing we can get out of options array bound if
the next character after array is delimiter. The patch adds a check
if we reach the end.

Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Reviewed-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: Steve Conklin <sconklin@canonical.com>