CVE-2026-52977 (GCVE-0-2026-52977)
Vulnerability from cvelistv5
Published
2026-06-24 16:28
Modified
2026-08-19 16:28
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: futex: Prevent lockup in requeue-PI during signal/ timeout wakeup During wait-requeue-pi (task A) and requeue-PI (task B) the following race can happen: Task A Task B futex_wait_requeue_pi() futex_setup_timer() futex_do_wait() futex_requeue() CLASS(hb, hb1)(&key1); CLASS(hb, hb2)(&key2); *timeout* futex_requeue_pi_wakeup_sync() requeue_state = Q_REQUEUE_PI_IGNORE *blocks on hb->lock* futex_proxy_trylock_atomic() futex_requeue_pi_prepare() Q_REQUEUE_PI_IGNORE => -EAGAIN double_unlock_hb(hb1, hb2) *retry* Task B acquires both hb locks and attempts to acquire the PI-lock of the top most waiter (task B). Task A is leaving early due to a signal/ timeout and started removing itself from the queue. It updates its requeue_state but can not remove it from the list because this requires the hb lock which is owned by task B. Usually task A is able to swoop the lock after task B unlocked it. However if task B is of higher priority then task A may not be able to wake up in time and acquire the lock before task B gets it again. Especially on a UP system where A is never scheduled. As a result task A blocks on the lock and task B busy loops, trying to make progress but live locks the system instead. Tragic. This can be fixed by removing the top most waiter from the list in this case. This allows task B to grab the next top waiter (if any) in the next iteration and make progress. Remove the top most waiter if futex_requeue_pi_prepare() fails. Let the waiter conditionally remove itself from the list in handle_early_requeue_pi_wakeup().
References
Impacted products
Vendor Product Version
Linux Linux Version: 07d91ef510fb16a2e0ca7453222105835b7ba3b8
Version: 07d91ef510fb16a2e0ca7453222105835b7ba3b8
Version: 07d91ef510fb16a2e0ca7453222105835b7ba3b8
Version: 07d91ef510fb16a2e0ca7453222105835b7ba3b8
Version: 07d91ef510fb16a2e0ca7453222105835b7ba3b8
Version: 07d91ef510fb16a2e0ca7453222105835b7ba3b8
Version: 07d91ef510fb16a2e0ca7453222105835b7ba3b8
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{
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Prevent lockup in requeue-PI during signal/ timeout wakeup\n\nDuring wait-requeue-pi (task A) and requeue-PI (task B) the following\nrace can happen:\n\n     Task A                             Task B\n  futex_wait_requeue_pi()\n    futex_setup_timer()\n    futex_do_wait()\n                                   futex_requeue()\n                                        CLASS(hb, hb1)(\u0026key1);\n                                        CLASS(hb, hb2)(\u0026key2);\n        *timeout*\n    futex_requeue_pi_wakeup_sync()\n        requeue_state = Q_REQUEUE_PI_IGNORE\n\n    *blocks on hb-\u003elock*\n\n                                        futex_proxy_trylock_atomic()\n                                          futex_requeue_pi_prepare()\n                                            Q_REQUEUE_PI_IGNORE =\u003e -EAGAIN\n                                        double_unlock_hb(hb1, hb2)\n                                         *retry*\n\nTask B acquires both hb locks and attempts to acquire the PI-lock of the\ntop most waiter (task B). Task A is leaving early due to a signal/\ntimeout and started removing itself from the queue. It updates its\nrequeue_state but can not remove it from the list because this requires\nthe hb lock which is owned by task B.\n\nUsually task A is able to swoop the lock after task B unlocked it.\nHowever if task B is of higher priority then task A may not be able to\nwake up in time and acquire the lock before task B gets it again.\nEspecially on a UP system where A is never scheduled.\n\nAs a result task A blocks on the lock and task B busy loops, trying to\nmake progress but live locks the system instead. Tragic.\n\nThis can be fixed by removing the top most waiter from the list in this\ncase. This allows task B to grab the next top waiter (if any) in the\nnext iteration and make progress.\n\nRemove the top most waiter if futex_requeue_pi_prepare() fails.\nLet the waiter conditionally remove itself from the list in\nhandle_early_requeue_pi_wakeup()."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-19T16:28:04.076Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/e5dbae3572757cecc3d3ec7cf96cbcc9cd9f016c"
        },
        {
          "url": "https://git.kernel.org/stable/c/4e0ed44e51727d56244a822ab941efe507c47966"
        },
        {
          "url": "https://git.kernel.org/stable/c/e3f95b1ba242e37093305812df7fdbe7288a43ac"
        },
        {
          "url": "https://git.kernel.org/stable/c/0aacb6d18f76552e3e0ee25d9f40d21b3486f4cf"
        },
        {
          "url": "https://git.kernel.org/stable/c/69a7cfc66405aeaa2483147653d031b3592ffc9c"
        },
        {
          "url": "https://git.kernel.org/stable/c/0304d60abb9dcc02bc7fe6d1850f4ca206e8f1a0"
        },
        {
          "url": "https://git.kernel.org/stable/c/bc7304f3ae20972d11db6e0b1b541c63feda5f05"
        }
      ],
      "title": "futex: Prevent lockup in requeue-PI during signal/ timeout wakeup",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
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  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-52977",
    "datePublished": "2026-06-24T16:28:53.937Z",
    "dateReserved": "2026-06-09T07:44:35.376Z",
    "dateUpdated": "2026-08-19T16:28:04.076Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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