futex: Fix race in futex_pivot_pending() during private hash resize

{
  "id": "bdcb5b42fe0dbcd5a39b542e956456cd15141b5f96f56f37d1a39c11f817e565",
  "url": "https://osv.dev/vulnerability/CVE-2026-80776",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "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 pos",
    "evidence": "osv:CVE-2026-80776",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.18.46",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.11",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-80776",
      "aliases": [
        "CVE-2026-80776"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "bd54df5ea7cadac520e346d5f0fe5d58e635b6ba"
                },
                {
                  "fixed": "4a7e941ca29a608c6244cbd028d3599ecaef7207"
                },
                {
                  "fixed": "19b4be0717fa83265d66aea836b7022d898422cf"
                },
                {
                  "fixed": "8e7ff730dd96519a333d1570edf1c3fabb6d3629"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80776.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.16.0"
                },
                {
                  "fixed": "6.18.46"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.1.11"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80776.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:28.802443015Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/19b4be0717fa83265d66aea836b7022d898422cf",
        "https://git.kernel.org/stable/c/4a7e941ca29a608c6244cbd028d3599ecaef7207",
        "https://git.kernel.org/stable/c/8e7ff730dd96519a333d1570edf1c3fabb6d3629",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80776.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-80776",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80776.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-80776",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 495823,
  "published_at": "2026-09-04T15:12:48.314+00:00"
}