GHSA-86FP-6JQC-QG25

Vulnerability from github – Published: 2025-12-04 18:30 – Updated: 2025-12-04 18:30
VLAI?
Details

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

mptcp: fix race condition in mptcp_schedule_work()

syzbot reported use-after-free in mptcp_schedule_work() [1]

Issue here is that mptcp_schedule_work() schedules a work, then gets a refcount on sk->sk_refcnt if the work was scheduled. This refcount will be released by mptcp_worker().

[A] if (schedule_work(...)) { [B] sock_hold(sk); return true; }

Problem is that mptcp_worker() can run immediately and complete before [B]

We need instead :

sock_hold(sk);
if (schedule_work(...))
    return true;
sock_put(sk);

[1] refcount_t: addition on 0; use-after-free. WARNING: CPU: 1 PID: 29 at lib/refcount.c:25 refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:25 Call Trace: __refcount_add include/linux/refcount.h:-1 [inline] __refcount_inc include/linux/refcount.h:366 [inline] refcount_inc include/linux/refcount.h:383 [inline] sock_hold include/net/sock.h:816 [inline] mptcp_schedule_work+0x164/0x1a0 net/mptcp/protocol.c:943 mptcp_tout_timer+0x21/0xa0 net/mptcp/protocol.c:2316 call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747 expire_timers kernel/time/timer.c:1798 [inline] __run_timers kernel/time/timer.c:2372 [inline] __run_timer_base+0x648/0x970 kernel/time/timer.c:2384 run_timer_base kernel/time/timer.c:2393 [inline] run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2403 handle_softirqs+0x22f/0x710 kernel/softirq.c:622 __do_softirq kernel/softirq.c:656 [inline] run_ktimerd+0xcf/0x190 kernel/softirq.c:1138 smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

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{
  "affected": [],
  "aliases": [
    "CVE-2025-40258"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-12-04T16:16:19Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmptcp: fix race condition in mptcp_schedule_work()\n\nsyzbot reported use-after-free in mptcp_schedule_work() [1]\n\nIssue here is that mptcp_schedule_work() schedules a work,\nthen gets a refcount on sk-\u003esk_refcnt if the work was scheduled.\nThis refcount will be released by mptcp_worker().\n\n[A] if (schedule_work(...)) {\n[B]     sock_hold(sk);\n        return true;\n    }\n\nProblem is that mptcp_worker() can run immediately and complete before [B]\n\nWe need instead :\n\n    sock_hold(sk);\n    if (schedule_work(...))\n        return true;\n    sock_put(sk);\n\n[1]\nrefcount_t: addition on 0; use-after-free.\n WARNING: CPU: 1 PID: 29 at lib/refcount.c:25 refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:25\nCall Trace:\n \u003cTASK\u003e\n __refcount_add include/linux/refcount.h:-1 [inline]\n  __refcount_inc include/linux/refcount.h:366 [inline]\n  refcount_inc include/linux/refcount.h:383 [inline]\n  sock_hold include/net/sock.h:816 [inline]\n  mptcp_schedule_work+0x164/0x1a0 net/mptcp/protocol.c:943\n  mptcp_tout_timer+0x21/0xa0 net/mptcp/protocol.c:2316\n  call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747\n  expire_timers kernel/time/timer.c:1798 [inline]\n  __run_timers kernel/time/timer.c:2372 [inline]\n  __run_timer_base+0x648/0x970 kernel/time/timer.c:2384\n  run_timer_base kernel/time/timer.c:2393 [inline]\n  run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2403\n  handle_softirqs+0x22f/0x710 kernel/softirq.c:622\n  __do_softirq kernel/softirq.c:656 [inline]\n  run_ktimerd+0xcf/0x190 kernel/softirq.c:1138\n  smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160\n  kthread+0x711/0x8a0 kernel/kthread.c:463\n  ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158\n  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245",
  "id": "GHSA-86fp-6jqc-qg25",
  "modified": "2025-12-04T18:30:53Z",
  "published": "2025-12-04T18:30:53Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-40258"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/035bca3f017ee9dea3a5a756e77a6f7138cc6eea"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3fc7723ed01d1130d4bf7063c50e0af60ecccbb4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8f9ba1a99a89feef9b5867c15a0141a97e893309"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ac28dfddedf6f209190950fc71bcff65ec4ab47b"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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