bpf: Add BPF_PROG_TYPE_CGROUP_SKB attach type enforcement in BPF_LINK_CREATE

{
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  "url": "https://www.cve.org/CVERecord?id=CVE-2024-38564",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "bpf: Add BPF_PROG_TYPE_CGROUP_SKB attach type enforcement in BPF_LINK_CREATE",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: bpf: Add BPF_PROG_TYPE_CGROUP_SKB attach type enforcement in BPF_LINK_CREATE bpf_prog_attach uses attach_type_to_prog_type to enforce proper attach type for BPF_PROG_TYPE_CGROUP_SKB. link_create uses bpf_prog_get and relies on bpf_prog_attach_check_attach_type to properly verify prog_type <> attach_type association. Add missing attach_type enforcement for the link_create case. Otherwise, it's currently possible to attach cgroup_skb prog types to other cgroup hooks.",
    "evidence": "cve:CVE-2024-38564",
    "products": [
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          "evidence": "/containers/cna/affected/0/product"
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        "fixed_versions": [],
        "affected_versions": []
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            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
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              "value": "AV:L - The flaw is reached exclusively through the `bpf(BPF_LINK_CREATE)` syscall and then triggered by an ordinary syscall (e.g. `getsockopt()`) from a process in the target cgroup. Per kernel guidance BPF is Local.\nAC:L - Exploitation is fully deterministic — the attacker authors the cgroup_skb program, chooses the mismatched attach type, picks the target cgroup, and invokes the hook itself; there is no race, no memory-layout dependency, and no special kernel config beyond stock `CONFIG_CGROUP_BPF`.\nPR:L - The attach path requires CAP_NET_ADMIN/CAP_SYS_ADMIN via `bpf_token_capable()`, which on 6.8+ is satisfied by `ns_capable(token->userns, CAP_NET_ADMIN)` — i.e. reachable by container-root inside a BPF-token-delegated user namespace, an unprivileged principal from the host's perspective, matching the PR:L treatment of other BPF-capability-gated kernel.org CVEs.\nUI:N - The attacker attaches the link and then triggers the confused hook from its own process; no action by any other user is required.\nS:U - The type confusion corrupts kernel memory within the same kernel security authority — a standard local privilege escalation with no VM, IOMMU, or sandbox boundary crossed.\nC:H - sk_buff-offset loads against a 12–56 byte stack ctx read kernel stack memory out of bounds, and skb helpers such as `bpf_skb_load_bytes()` dereference wild pointers harvested from that memory, yielding effectively arbitrary kernel memory disclosure exfiltrated through BPF maps.\nI:H - `cg_skb_is_valid_access` permits writes to `__sk_buff->mark`, `->priority` and `->cb[0..4]`, which compile to raw stores ~0x30–0xa8 bytes past the small stack ctx, giving attacker-controlled out-of-bounds kernel stack writes into caller frames — a control-flow hijack primitive.\nA:H - The wild-pointer dereferences and stack corruption reliably produce a general protection fault, KASAN splat, or panic — this is exactly how syzbot (`syzbot+838346b979830606c854`) surfaced the bug."
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      "modified": "2026-10-27T15:53:48.399Z",
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  "source_id": "core-cve",
  "document_id": 394428,
  "published_at": "2024-06-19T13:35:32.222+00:00"
}