futex: Fix race in futex_pivot_pending() during private hash resize
Summary
| CVE | CVE-2026-80776 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-04 16:18:03 UTC |
| Updated | 2026-09-04 16:18:03 UTC |
| Description | 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. |
Risk And Classification
EPSS: 0.001660000 probability, percentile 0.061100000 (date 2026-09-07)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected bd54df5ea7cadac520e346d5f0fe5d58e635b6ba 4a7e941ca29a608c6244cbd028d3599ecaef7207 git | Not specified |
| CNA | Linux | Linux | affected bd54df5ea7cadac520e346d5f0fe5d58e635b6ba 19b4be0717fa83265d66aea836b7022d898422cf git | Not specified |
| CNA | Linux | Linux | affected bd54df5ea7cadac520e346d5f0fe5d58e635b6ba 8e7ff730dd96519a333d1570edf1c3fabb6d3629 git | Not specified |
| CNA | Linux | Linux | affected 6.16 | Not specified |
| CNA | Linux | Linux | unaffected 6.16 semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.46 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.1.11 7.1.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.2 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/8e7ff730dd96519a333d1570edf1c3fabb6d3629 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/19b4be0717fa83265d66aea836b7022d898422cf | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/4a7e941ca29a608c6244cbd028d3599ecaef7207 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.