CVE-2026-68299

In the Linux kernel, the following vulnerability has been resolved:

vmxnet3: fix BUGON in vmxnet3gethdrlen() for Geneve packets

vmxnet3gethdrlen() 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 VMXNET3RCDHDRINNER_SHIFT bit in the completion descriptor. Since the function never skips the outer encapsulation, this mismatch triggers:

• BUGON(hdr.ipv4->protocol != IPPROTOTCP), because the outer protocol is UDP (Geneve), not TCP.
• BUGON(hdr.eth->hproto != ...), when the tunnel's outer and inner IP versions differ (e.g. outer IPv6/inner IPv4 or vice versa).

Check VMXNET3RCDHDRINNERSHIFT 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.