CVE-2026-80776 (GCVE-0-2026-80776)

Vulnerability from cvelistv5 – Published: 2026-09-04 15:12 – Updated: 2026-09-04 15:12
VLAI
Title
futex: Fix race in futex_pivot_pending() during private hash resize
Summary
In the Linux kernel, the following vulnerability has been resolved: futex: Fix race in futex_pivot_pending() during private hash resize A task performing a custom private hash resize can remain blocked in uninterruptible sleep indefinitely. The hung-task detector reports: INFO: task futex-resizer:314 blocked for more than 10 seconds. task:futex-resizer state:D stack:14824 pid:314 tgid:312 ppid:311 Call Trace: __schedule+0x521/0xf30 schedule+0x22/0xa0 futex_hash_allocate+0x3db/0x490 __do_sys_prctl+0x6f5/0xbd0 do_syscall_64+0xf9/0x530 entry_SYSCALL_64_after_hwframe+0x77/0x7f Kernel panic - not syncing: hung_task: blocked tasks futex_pivot_pending() allows the resize request to continue when either no replacement hash is pending (hash_new == NULL) or the current hash reference count has reached zero. After the final-reference wake, another futex task can complete the pivot between the two observations: T1 T2 futex_hash_allocate() wait_var_event(mm, ...) futex_pivot_pending(mm) hash_new != NULL futex_hash() futex_ref_get(old) -> false futex_pivot_hash(mm) hash_new = NULL __futex_pivot_hash(mm, new) rcu_assign_pointer(hash, new) fph = rcu_dereference(hash) /* new */ futex_ref_is_dead(fph) -> false schedule() The pivot changes the state from hash_new != NULL with a dead current hash to hash_new == NULL with a live current hash. Because futex_pivot_pending() reads hash_new and hash without serialization, the resize task can observe hash_new in the pre-pivot state and hash in the post-pivot state, causing futex_pivot_pending() to return false even though the pivot has completed. The task then goes to sleep after the wakeup has already been consumed. Serialize state reads in futex_pivot_pending() using futex_mm_phash::lock. This guarantees that futex_pivot_pending() observes hash_new and hash atomically, eliminating the race condition.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: bd54df5ea7cadac520e346d5f0fe5d58e635b6ba , < 4a7e941ca29a608c6244cbd028d3599ecaef7207 (git)
Affected: bd54df5ea7cadac520e346d5f0fe5d58e635b6ba , < 19b4be0717fa83265d66aea836b7022d898422cf (git)
Affected: bd54df5ea7cadac520e346d5f0fe5d58e635b6ba , < 8e7ff730dd96519a333d1570edf1c3fabb6d3629 (git)
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Linux Linux Affected: 6.16
Unaffected: 0 , < 6.16 (semver)
Unaffected: 6.18.46 , ≤ 6.18.* (semver)
Unaffected: 7.1.11 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
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          "vendor": "Linux",
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Fix race in futex_pivot_pending() during private hash resize\n\nA task performing a custom private hash resize can remain blocked in\nuninterruptible sleep indefinitely.  The hung-task detector reports:\n\n  INFO: task futex-resizer:314 blocked for more than 10 seconds.\n  task:futex-resizer state:D stack:14824 pid:314 tgid:312 ppid:311\n\n  Call Trace:\n   __schedule+0x521/0xf30\n   schedule+0x22/0xa0\n   futex_hash_allocate+0x3db/0x490\n   __do_sys_prctl+0x6f5/0xbd0\n   do_syscall_64+0xf9/0x530\n   entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\n  Kernel panic - not syncing: hung_task: blocked tasks\n\nfutex_pivot_pending() allows the resize request to continue when\neither no replacement hash is pending (hash_new == NULL) or the current\nhash reference count has reached zero.\n\nAfter the final-reference wake, another futex task can complete the\npivot between the two observations:\n\n  T1                                  T2\n\n  futex_hash_allocate()\n    wait_var_event(mm, ...)\n      futex_pivot_pending(mm)\n        hash_new != NULL\n                                      futex_hash()\n                                        futex_ref_get(old) -\u003e false\n                                        futex_pivot_hash(mm)\n                                          hash_new = NULL\n                                          __futex_pivot_hash(mm, new)\n                                            rcu_assign_pointer(hash, new)\n        fph = rcu_dereference(hash) /* new */\n        futex_ref_is_dead(fph) -\u003e false\n      schedule()\n\nThe pivot changes the state from hash_new != NULL with a dead current\nhash to hash_new == NULL with a live current hash.  Because\nfutex_pivot_pending() reads hash_new and hash without serialization,\nthe resize task can observe hash_new in the pre-pivot state and hash in\nthe post-pivot state, causing futex_pivot_pending() to return false even\nthough the pivot has completed.  The task then goes to sleep after the\nwakeup has already been consumed.\n\nSerialize state reads in futex_pivot_pending() using futex_mm_phash::lock.\nThis guarantees that futex_pivot_pending() observes hash_new and hash\natomically, eliminating the race condition."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-04T15:12:48.314Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/4a7e941ca29a608c6244cbd028d3599ecaef7207"
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          "url": "https://git.kernel.org/stable/c/19b4be0717fa83265d66aea836b7022d898422cf"
        },
        {
          "url": "https://git.kernel.org/stable/c/8e7ff730dd96519a333d1570edf1c3fabb6d3629"
        }
      ],
      "title": "futex: Fix race in futex_pivot_pending() during private hash resize",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-80776",
    "datePublished": "2026-09-04T15:12:48.314Z",
    "dateReserved": "2026-08-26T14:34:25.792Z",
    "dateUpdated": "2026-09-04T15:12:48.314Z",
    "state": "PUBLISHED"
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      "date": "2026-10-03",
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      "percentile": "0.09649"
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                    "version": "7.1.11",
                    "versionType": "semver"
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        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Fix race in futex_pivot_pending() during private hash resize\n\nA task performing a custom private hash resize can remain blocked in\nuninterruptible sleep indefinitely.  The hung-task detector reports:\n\n  INFO: task futex-resizer:314 blocked for more than 10 seconds.\n  task:futex-resizer state:D stack:14824 pid:314 tgid:312 ppid:311\n\n  Call Trace:\n   __schedule+0x521/0xf30\n   schedule+0x22/0xa0\n   futex_hash_allocate+0x3db/0x490\n   __do_sys_prctl+0x6f5/0xbd0\n   do_syscall_64+0xf9/0x530\n   entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\n  Kernel panic - not syncing: hung_task: blocked tasks\n\nfutex_pivot_pending() allows the resize request to continue when\neither no replacement hash is pending (hash_new == NULL) or the current\nhash reference count has reached zero.\n\nAfter the final-reference wake, another futex task can complete the\npivot between the two observations:\n\n  T1                                  T2\n\n  futex_hash_allocate()\n    wait_var_event(mm, ...)\n      futex_pivot_pending(mm)\n        hash_new != NULL\n                                      futex_hash()\n                                        futex_ref_get(old) -\u003e false\n                                        futex_pivot_hash(mm)\n                                          hash_new = NULL\n                                          __futex_pivot_hash(mm, new)\n                                            rcu_assign_pointer(hash, new)\n        fph = rcu_dereference(hash) /* new */\n        futex_ref_is_dead(fph) -\u003e false\n      schedule()\n\nThe pivot changes the state from hash_new != NULL with a dead current\nhash to hash_new == NULL with a live current hash.  Because\nfutex_pivot_pending() reads hash_new and hash without serialization,\nthe resize task can observe hash_new in the pre-pivot state and hash in\nthe post-pivot state, causing futex_pivot_pending() to return false even\nthough the pivot has completed.  The task then goes to sleep after the\nwakeup has already been consumed.\n\nSerialize state reads in futex_pivot_pending() using futex_mm_phash::lock.\nThis guarantees that futex_pivot_pending() observes hash_new and hash\natomically, eliminating the race condition."
          }
        ],
        "id": "CVE-2026-80776",
        "lastModified": "2026-09-04T16:18:03.250",
        "metrics": {},
        "published": "2026-09-04T16:18:03.250",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/19b4be0717fa83265d66aea836b7022d898422cf"
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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            "url": "https://git.kernel.org/stable/c/8e7ff730dd96519a333d1570edf1c3fabb6d3629"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    }
  }
}



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