xprtrdma: Decouple req recycling from RPC completion

{
  "id": "58c2a0e5ba35c6590dcee1962e048f8490b27d5a3a1769ffee40f9916c77a18e",
  "url": "https://osv.dev/vulnerability/CVE-2026-72473",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "xprtrdma: Decouple req recycling from RPC completion",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: xprtrdma: Decouple req recycling from RPC completion rl_kref formerly served two distinct lifetimes through a single refcount: it gated when a Reply could wake its RPC task, and it gated when an rpcrdma_req could return to its free pool. The marshal path took the Send-side reference only when SGEs needed DMA-unmap (sc_unmap_count > 0), which made a Send carrying only pre-registered buffers an exception: the Reply handler dropped rl_kref from 1 to 0 and freed the req while the HCA might still be DMA-reading from its send buffer. Give rl_kref a narrower job. The RPC layer takes one reference when slot allocation hands a req out. rpcrdma_prepare_send_sges() takes a Send-side reference unconditionally after WR preparation succeeds. xprt_rdma_free_slot() and xprt_rdma_bc_free_rqst() drop the RPC-layer reference; rpcrdma_sendctx_unmap() drops the Send-side reference. The req returns to its free pool only after both owners have signed off. The existing kref_init(&req->rl_kref) call in rpcrdma_prepare_send_sges() is removed. Initialization moves to the slot-allocation paths (xprt_rdma_alloc_slot and rpcrdma_bc_rqst_get), and the release callback re-arms rl_kref before the req returns to a free pool. A re-init in the marshal path would discard the RPC-layer reference that already exists on entry. Three invariants follow: - Any rpcrdma_req held by an rpc_rqst has rl_kref >= 1. xprt_rdma_alloc_slot(), rpcrdma_bc_rqst_ge",
    "evidence": "osv:CVE-2026-72473",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
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            "value": "6.1.178",
            "evidence": "/affected/1/ranges"
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            "value": "6.6.145",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.97",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.40",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.5",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-72473",
      "aliases": [
        "CVE-2026-72473"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
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            "name": "Kernel",
            "ecosystem": "Linux"
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            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-72473.json"
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      ],
      "modified": "2026-10-28T02:30:22.034147732Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/53442c7d0c888e51b8bc3da196970a669cc6b294",
        "https://git.kernel.org/stable/c/740975054a1970c0cf15f70ac39724a064f45847",
        "https://git.kernel.org/stable/c/8203f760a72bd39a3b66bc4eff0aa272a99fe22b",
        "https://git.kernel.org/stable/c/9f3d9b68c1c6c51746e5ecdb52b2e6a2901de37e",
        "https://git.kernel.org/stable/c/e7632089523acddcdd8f090ad19e96fb3107b04d",
        "https://git.kernel.org/stable/c/e786233d2e0bbff9a82e43f02ae3a46ab4b08ec3",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72473.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-72473",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72473.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-72473",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 488348,
  "published_at": "2026-08-15T05:57:14.412+00:00"
}