GHSA-8F6M-26FJ-7FM5

Vulnerability from github – Published: 2024-04-25 06:30 – Updated: 2025-12-23 21:30
VLAI?
Details

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

af_unix: Fix garbage collector racing against connect()

Garbage collector does not take into account the risk of embryo getting enqueued during the garbage collection. If such embryo has a peer that carries SCM_RIGHTS, two consecutive passes of scan_children() may see a different set of children. Leading to an incorrectly elevated inflight count, and then a dangling pointer within the gc_inflight_list.

sockets are AF_UNIX/SOCK_STREAM S is an unconnected socket L is a listening in-flight socket bound to addr, not in fdtable V's fd will be passed via sendmsg(), gets inflight count bumped

connect(S, addr) sendmsg(S, [V]); close(V) __unix_gc() ---------------- ------------------------- -----------

NS = unix_create1() skb1 = sock_wmalloc(NS) L = unix_find_other(addr) unix_state_lock(L) unix_peer(S) = NS // V count=1 inflight=0

        NS = unix_peer(S)
        skb2 = sock_alloc()
        skb_queue_tail(NS, skb2[V])

        // V became in-flight
        // V count=2 inflight=1

        close(V)

        // V count=1 inflight=1
        // GC candidate condition met

                    for u in gc_inflight_list:
                      if (total_refs == inflight_refs)
                        add u to gc_candidates

                    // gc_candidates={L, V}

                    for u in gc_candidates:
                      scan_children(u, dec_inflight)

                    // embryo (skb1) was not
                    // reachable from L yet, so V's
                    // inflight remains unchanged

__skb_queue_tail(L, skb1) unix_state_unlock(L) for u in gc_candidates: if (u.inflight) scan_children(u, inc_inflight_move_tail)

                    // V count=1 inflight=2 (!)

If there is a GC-candidate listening socket, lock/unlock its state. This makes GC wait until the end of any ongoing connect() to that socket. After flipping the lock, a possibly SCM-laden embryo is already enqueued. And if there is another embryo coming, it can not possibly carry SCM_RIGHTS. At this point, unix_inflight() can not happen because unix_gc_lock is already taken. Inflight graph remains unaffected.

Severity ?
4.7 (Medium)
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Show details on source website
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{
  "affected": [],
  "aliases": [
    "CVE-2024-26923"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-362"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-04-25T06:15:57Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\naf_unix: Fix garbage collector racing against connect()\n\nGarbage collector does not take into account the risk of embryo getting\nenqueued during the garbage collection. If such embryo has a peer that\ncarries SCM_RIGHTS, two consecutive passes of scan_children() may see a\ndifferent set of children. Leading to an incorrectly elevated inflight\ncount, and then a dangling pointer within the gc_inflight_list.\n\nsockets are AF_UNIX/SOCK_STREAM\nS is an unconnected socket\nL is a listening in-flight socket bound to addr, not in fdtable\nV\u0027s fd will be passed via sendmsg(), gets inflight count bumped\n\nconnect(S, addr)\tsendmsg(S, [V]); close(V)\t__unix_gc()\n----------------\t-------------------------\t-----------\n\nNS = unix_create1()\nskb1 = sock_wmalloc(NS)\nL = unix_find_other(addr)\nunix_state_lock(L)\nunix_peer(S) = NS\n\t\t\t// V count=1 inflight=0\n\n \t\t\tNS = unix_peer(S)\n \t\t\tskb2 = sock_alloc()\n\t\t\tskb_queue_tail(NS, skb2[V])\n\n\t\t\t// V became in-flight\n\t\t\t// V count=2 inflight=1\n\n\t\t\tclose(V)\n\n\t\t\t// V count=1 inflight=1\n\t\t\t// GC candidate condition met\n\n\t\t\t\t\t\tfor u in gc_inflight_list:\n\t\t\t\t\t\t  if (total_refs == inflight_refs)\n\t\t\t\t\t\t    add u to gc_candidates\n\n\t\t\t\t\t\t// gc_candidates={L, V}\n\n\t\t\t\t\t\tfor u in gc_candidates:\n\t\t\t\t\t\t  scan_children(u, dec_inflight)\n\n\t\t\t\t\t\t// embryo (skb1) was not\n\t\t\t\t\t\t// reachable from L yet, so V\u0027s\n\t\t\t\t\t\t// inflight remains unchanged\n__skb_queue_tail(L, skb1)\nunix_state_unlock(L)\n\t\t\t\t\t\tfor u in gc_candidates:\n\t\t\t\t\t\t  if (u.inflight)\n\t\t\t\t\t\t    scan_children(u, inc_inflight_move_tail)\n\n\t\t\t\t\t\t// V count=1 inflight=2 (!)\n\nIf there is a GC-candidate listening socket, lock/unlock its state. This\nmakes GC wait until the end of any ongoing connect() to that socket. After\nflipping the lock, a possibly SCM-laden embryo is already enqueued. And if\nthere is another embryo coming, it can not possibly carry SCM_RIGHTS. At\nthis point, unix_inflight() can not happen because unix_gc_lock is already\ntaken. Inflight graph remains unaffected.",
  "id": "GHSA-8f6m-26fj-7fm5",
  "modified": "2025-12-23T21:30:16Z",
  "published": "2024-04-25T06:30:35Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-26923"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2e2a03787f4f0abc0072350654ab0ef3324d9db3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/343c5372d5e17b306db5f8f3c895539b06e3177f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/47d8ac011fe1c9251070e1bd64cb10b48193ec51"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/507cc232ffe53a352847893f8177d276c3b532a9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a36ae0ec2353015f0f6762e59f4c2dbc0c906423"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b75722be422c276b699200de90527d01c602ea7c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/dbdf7bec5c920200077d693193f989cb1513f009"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e76c2678228f6aec74b305ae30c9374cc2f28a51"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2024/06/msg00020.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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Detection rules are retrieved from Rulezet.