ghsa-fwvg-7877-39cm
Vulnerability from github
Published
2025-05-16 15:31
Modified
2025-11-03 21:33
Details

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

net_sched: hfsc: Fix a UAF vulnerability in class with netem as child qdisc

As described in Gerrard's report [1], we have a UAF case when an hfsc class has a netem child qdisc. The crux of the issue is that hfsc is assuming that checking for cl->qdisc->q.qlen == 0 guarantees that it hasn't inserted the class in the vttree or eltree (which is not true for the netem duplicate case).

This patch checks the n_active class variable to make sure that the code won't insert the class in the vttree or eltree twice, catering for the reentrant case.

[1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/

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{
  "affected": [],
  "aliases": [
    "CVE-2025-37890"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-05-16T13:15:52Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: hfsc: Fix a UAF vulnerability in class with netem as child qdisc\n\nAs described in Gerrard\u0027s report [1], we have a UAF case when an hfsc class\nhas a netem child qdisc. The crux of the issue is that hfsc is assuming\nthat checking for cl-\u003eqdisc-\u003eq.qlen == 0 guarantees that it hasn\u0027t inserted\nthe class in the vttree or eltree (which is not true for the netem\nduplicate case).\n\nThis patch checks the n_active class variable to make sure that the code\nwon\u0027t insert the class in the vttree or eltree twice, catering for the\nreentrant case.\n\n[1] https://lore.kernel.org/netdev/CAHcdcOm+03OD2j6R0=YHKqmy=VgJ8xEOKuP6c7mSgnp-TEJJbw@mail.gmail.com/",
  "id": "GHSA-fwvg-7877-39cm",
  "modified": "2025-11-03T21:33:54Z",
  "published": "2025-05-16T15:31:02Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-37890"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/141d34391abbb315d68556b7c67ad97885407547"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/273bbcfa53541cde38b2003ad88a59b770306421"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2e7093c7a8aba5d4f8809f271488e5babe75e202"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6082a87af4c52f58150d40dec1716011d871ac21"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8df7d37d626430035b413b97cee18396b3450bef"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ac39fd4a757584d78ed062d4f6fd913f83bd98b5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e0cf8ee23e1915431f262a7b2dee0c7a7d699af0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e3e949a39a91d1f829a4890e7dfe9417ac72e4d0"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/08/msg00010.html"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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