tap: add missing verification for short frame

In the Linux kernel, the following vulnerability has been resolved: tap: add missing verification for short frame The cited commit missed to check against the validity of the frame length in the tap_get_user_xdp() path, which could cause a corrupted skb to be sent downstack. Even before the skb is transmitted, the tap_get_user_xdp()-->skb_set_network_header() may assume the size is more than ETH_HLEN. Once transmitted, this could either cause out-of-bound access beyond the actual length, or confuse the underlayer with incorrect or inconsistent header length in the skb metadata. In the alternative path, tap_get_user() already prohibits short frame which has the length less than Ethernet header size from being transmitted. This is to drop any frame shorter than the Ethernet header size just like how tap_get_user() does. CVE: CVE-2024-41090