{"id":"CVE-2026-90003","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-90003","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Prevent rcuwait use-after-free during requeue PI\n\nOn PREEMPT_RT, FUTEX_CMP_REQUEUE_PI can trigger a KASAN…","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Prevent rcuwait use-after-free during requeue PI\n\nOn PREEMPT_RT, FUTEX_CMP_REQUEUE_PI can trigger a KASAN report\n(slab-out-of-bounds) in futex_requeue_pi_complete() invocation of\nrcuwait_wake_up().\n\nThe futex_q used by futex_wait_requeue_pi() is allocated on the waiter's\nstack. An early wakeup can race with a PI requeue as follows:\n\n        waiter                          requeue task\n        ------                          ------------\nfutex_wait_requeue_pi()\n  futex_do_wait()\n    schedule()\n                                       futex_requeue\n                                         futex_proxy_trylock_atomic()\n                                           futex_requeue_pi_prepare()\n                                            Q_REQUEUE_PI_NONE -> Q_REQUEUE_PI_IN_PROGRESS\n* timeout/ signal wakes waiter *\n  futex_requeue_pi_wakeup_sync()\n   Q_REQUEUE_PI_IN_PROGRESS -> Q_REQUEUE_PI_WAIT\n                                           requeue_pi_wake_futex\n                                             futex_requeue_pi_complete()\n                                               cmpxchg Q_REQUEUE_PI_WAIT -> Q_REQUEUE_PI_LOCKED\n    rcuwait_wait_event()\n      if (atomic_read(&q->requeue_state) != Q_REQUEUE_PI_WAIT)\n       break /* no schedule() */\n\n /* q.pi_state->owner == current */\n futex_private_hash_put()\n /* return from syscall */\n                                              rcuwait_wake_up(&q->requeue_wait)\n                                                /* q is gone */\n\nfutex_requeue_pi_complete() publishes Q_REQUEUE_PI_LOCKED before\ncalling rcuwait_wake_up(). The waiter observes this state in\nrcuwait_wait_event() before invoking schedule() in rcuwait_wait_event().\nHere, the waiter is free leave the syscall before requeue task can\ncomplete the wake.\n\nTo address this race skip rcuwait_wake_up() in the Q_REQUEUE_PI_LOCKED\ncase.\nThis state is only published by requeue_pi_wake_futex(), which saves\nq->task before futex_requeue_pi_complete() and wakes the waiter via\nwake_up_state().\n\nThis wake is intended to wake the waiter from its futex_do_wait() sleep.\nIf the waiter is still sleeping there, it can not get into the\nQ_REQUEUE_PI_WAIT state (and require this removed wake).\nShould the waiter be woken up from futex_do_wait() by other means (as in\nthis example) and sleep in futex_requeue_pi_wakeup_sync() then the\nwake_up_state() from requeue_pi_wake_futex() will wake it, too.\nShould the waiter task terminate before wake_up_state() had a chance to\nwake the task then the task pointer does not become invalid because the\nfutex_hash_bucket::lock is held and the task pointer is RCU protected.\n\n[bigeasy: Updated comment and commit message]","published":"2026-09-16T11:17:12.810","modified":"2026-09-16T11:17:12.810","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/220ee9e04ca3b7f014c000264aa6c884f036c86e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/244f301759fd34b1dd0b4192ce44f8ef224e027d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7d1559126d86be6e4f6a85663dfbfe85caa47e37"},{"type":"WEB","url":"https://git.kernel.org/stable/c/81aadbd09bf1dcd3238212f336ba699503557ae8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a3b8d46fe401cba3a5c46dea610e6eb3dc15370e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e4a4ccfa470f910b747b3ee8d18670ed8ac8a236"}],"provenance":{"sources":["OSV.dev","NVD","FIRST.org (EPSS)"],"lastVerified":"2026-09-16T11:17:12.810"}}