CVE-2012-3360: OpenStack Nova Directory traversal vulnerability

The vulnerability stems from improper path sanitization in the file injection mechanism. The original implementation of _inject_file_into_fs in api.py used os.path.join(fs, path.lstrip('/')) without resolving symlinks or checking for traversal. The fix introduced _join_and_check_path_within_fs to normalize paths and ensure they stay within the guest filesystem. The commit message explicitly states this addresses CVE-2012-3360, and the diff shows _inject_file_into_fs was modified to use the new safety check. Unit tests added in test_virt.py verify that paths with '..' are rejected, confirming the vulnerable function's behavior before patching.