Medium [CVE-2026-68299] fix BUG_ON in vmxnet3_get_hdr_len for Geneve packets

In the Linux kernel, the following vulnerability has been resolved: vmxnet3: fix BUG_ON in vmxnet3_get_hdr_len() for Geneve packets vmxnet3_get_hdr_len() assumes gdesc->rcd.v4/v6/tcp always describe the outer header, but for a Geneve-encapsulated packet the device can set them based on the inner header instead, signalled by the VMXNET3_RCD_HDR_INNER_SHIFT bit in the completion descriptor.

Since the function never skips the outer encapsulation, this mismatch triggers: - BUG_ON(hdr.ipv4->protocol!= IPPROTO_TCP), because the outer protocol is UDP (Geneve), not TCP. - BUG_ON(hdr.eth->h_proto!=...), when the tunnel's outer and inner IP versions differ (e.g. outer IPv6/inner IPv4 or vice versa).

Check VMXNET3_RCD_HDR_INNER_SHIFT up front and bail out, since the function cannot locate the inner header it would need to parse. Also convert the remaining BUG_ON()s in this function to return 0 defensively.

A flaw was found in the `vmxnet3` virtual network device driver within the Linux kernel. When processing Geneve-encapsulated packets, the `vmxnet3_get_hdr_len()` function can incorrectly interpret header information, leading to a mismatch between expected and actual packet protocols or IP versions.

This can trigger a `BUG_ON` condition, resulting in a kernel panic and a system crash, effectively causing a Denial of Service (DoS).