bpf: Check skb->transport_header is set in bpf_skb_check_mtu

{
  "id": "241e9f122d31d2da6a8e584b23aa9ce592158c2affeadb168f8722262c658a8f",
  "url": "https://osv.dev/vulnerability/CVE-2025-68363",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "bpf: Check skb->transport_header is set in bpf_skb_check_mtu",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: bpf: Check skb->transport_header is set in bpf_skb_check_mtu The bpf_skb_check_mtu helper needs to use skb->transport_header when the BPF_MTU_CHK_SEGS flag is used: bpf_skb_check_mtu(skb, ifindex, &mtu_len, 0, BPF_MTU_CHK_SEGS) The transport_header is not always set. There is a WARN_ON_ONCE report when CONFIG_DEBUG_NET is enabled + skb->gso_size is set + bpf_prog_test_run is used: WARNING: CPU: 1 PID: 2216 at ./include/linux/skbuff.h:3071 skb_gso_validate_network_len bpf_skb_check_mtu bpf_prog_3920e25740a41171_tc_chk_segs_flag # A test in the next patch bpf_test_run bpf_prog_test_run_skb For a normal ingress skb (not test_run), skb_reset_transport_header is performed but there is plan to avoid setting it as described in commit 2170a1f09148 (\"net: no longer reset transport_header in __netif_receive_skb_core()\"). This patch fixes the bpf helper by checking skb_transport_header_was_set(). The check is done just before skb->transport_header is used, to avoid breaking the existing bpf prog. The WARN_ON_ONCE is limited to bpf_prog_test_run, so targeting bpf-next.",
    "evidence": "osv:CVE-2025-68363",
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      "modified": "2026-10-28T02:30:39.608939848Z",
      "provider": "osv",
      "references": [
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        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/68xxx/CVE-2025-68363.json",
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  "source_id": "core-osv",
  "document_id": 506889,
  "published_at": "2025-12-24T10:32:51.236+00:00"
}