GHSA-6RQW-4VWJ-WW2R

Vulnerability from github – Published: 2026-10-06 09:31 – Updated: 2026-10-07 09:32
VLAI
Details

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

RDMA/ucma: Serialize join and leave on copy_to_user failure

rdma_join_multicast() queues RoCE work that later reads the ucma_multicast through event->param.ud.private_data, then list_add()s the CMA multicast at the head of id_priv->mc_list. rdma_leave_multicast() matches only by sockaddr and destroys the first hit.

ucma_process_join() used to drop ctx->mutex after a successful join and retake it only if copy_to_user() failed. Two concurrent JOIN_MCAST calls with the same address can therefore insert a second CMA entry before the first thread's leave. leave then cancels the newer work and the older worker still dereferences the ucma_multicast that the first thread frees.

Keep ctx->mutex held from rdma_join_multicast() through copy_to_user() and, on -EFAULT, through rdma_leave_multicast() so leave cannot miss this join. Do not leave if join itself failed: that path never published this address on mc_list, and a leave-by-addr would destroy an earlier successful join.

Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-98253"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-06T09:18:13Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nRDMA/ucma: Serialize join and leave on copy_to_user failure\n\nrdma_join_multicast() queues RoCE work that later reads the ucma_multicast\nthrough event-\u003eparam.ud.private_data, then list_add()s the CMA multicast\nat the head of id_priv-\u003emc_list. rdma_leave_multicast() matches only by\nsockaddr and destroys the first hit.\n\nucma_process_join() used to drop ctx-\u003emutex after a successful join and\nretake it only if copy_to_user() failed. Two concurrent JOIN_MCAST calls\nwith the same address can therefore insert a second CMA entry before the\nfirst thread\u0027s leave. leave then cancels the newer work and the older\nworker still dereferences the ucma_multicast that the first thread frees.\n\nKeep ctx-\u003emutex held from rdma_join_multicast() through copy_to_user() and,\non -EFAULT, through rdma_leave_multicast() so leave cannot miss this join.\nDo not leave if join itself failed: that path never published this address\non mc_list, and a leave-by-addr would destroy an earlier successful join.",
  "id": "GHSA-6rqw-4vwj-ww2r",
  "modified": "2026-10-07T09:32:14Z",
  "published": "2026-10-06T09:31:32Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98253"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/01cbdb724c584d7772fd25af2e4dfdf8527ce0d5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/01e29d0d78a8f66f221625720a04939eef5ec1f6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/29b9ed83d8bfab5c6e11fcbf1aa836aa4ae26cb9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/43c4e24bd10370fc976f6220518049ce71419399"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/52172e11bd074ccaded21740ffeb67123f01dd00"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/662ade4de9ff5eceb0820a9f8e9fac70ba6a815b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/83610ee5e498fa5bfcb80031d2b959baea276bf6"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ae805d204cf1f15b87d1bf3529b4c649f3519420"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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