futex: Prevent lockup in requeue-PI during signal/ timeout wakeup
Summary
| CVE | CVE-2026-52977 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-06-24 17:17:08 UTC |
| Updated | 2026-06-24 17:17:08 UTC |
| Description | 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(). |
Risk And Classification
EPSS: 0.001720000 probability, percentile 0.068950000 (date 2026-06-29)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected 07d91ef510fb16a2e0ca7453222105835b7ba3b8 4e0ed44e51727d56244a822ab941efe507c47966 git | Not specified |
| CNA | Linux | Linux | affected 07d91ef510fb16a2e0ca7453222105835b7ba3b8 e3f95b1ba242e37093305812df7fdbe7288a43ac git | Not specified |
| CNA | Linux | Linux | affected 07d91ef510fb16a2e0ca7453222105835b7ba3b8 0aacb6d18f76552e3e0ee25d9f40d21b3486f4cf git | Not specified |
| CNA | Linux | Linux | affected 07d91ef510fb16a2e0ca7453222105835b7ba3b8 69a7cfc66405aeaa2483147653d031b3592ffc9c git | Not specified |
| CNA | Linux | Linux | affected 07d91ef510fb16a2e0ca7453222105835b7ba3b8 0304d60abb9dcc02bc7fe6d1850f4ca206e8f1a0 git | Not specified |
| CNA | Linux | Linux | affected 07d91ef510fb16a2e0ca7453222105835b7ba3b8 bc7304f3ae20972d11db6e0b1b541c63feda5f05 git | Not specified |
| CNA | Linux | Linux | affected 5.15 | Not specified |
| CNA | Linux | Linux | unaffected 5.15 semver | Not specified |
| CNA | Linux | Linux | unaffected 6.1.175 6.1.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.6.141 6.6.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.12.91 6.12.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.33 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.0.10 7.0.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.1 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/69a7cfc66405aeaa2483147653d031b3592ffc9c | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/bc7304f3ae20972d11db6e0b1b541c63feda5f05 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/e3f95b1ba242e37093305812df7fdbe7288a43ac | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/4e0ed44e51727d56244a822ab941efe507c47966 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/0304d60abb9dcc02bc7fe6d1850f4ca206e8f1a0 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/0aacb6d18f76552e3e0ee25d9f40d21b3486f4cf | 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.