futex: Prevent rcuwait use-after-free during requeue PI
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 6.1.188, 6.6.157, 6.12.110, 6.18.51, 7.2.5
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
In the Linux kernel, the following vulnerability has been resolved: futex: Prevent rcuwait use-after-free during requeue PI On PREEMPT_RT, FUTEX_CMP_REQUEUE_PI can trigger a KASAN report (slab-out-of-bounds) in futex_requeue_pi_complete() invocation of rcuwait_wake_up(). The futex_q used by futex_wait_requeue_pi() is allocated on the waiter's stack. An early wakeup can race with a PI requeue as follows: waiter requeue task ------ ------------ futex_wait_requeue_pi() futex_do_wait() schedule() futex_requeue futex_proxy_trylock_atomic() futex_requeue_pi_prepare() Q_REQUEUE_PI_NONE -> Q_REQUEUE_PI_IN_PROGRESS • timeout/ signal wakes waiter * futex_requeue_pi_wakeup_sync() Q_REQUEUE_PI_IN_PROGRESS -> Q_REQUEUE_PI_WAIT requeue_pi_wake_futex futex_requeue_pi_complete() cmpxchg Q_REQUEUE_PI_WAIT -> Q_REQUEUE_PI_LOCKED rcuwait_wait_event() if (atomic_read(&q->requeue_state) != Q_REQUEUE_PI_WAIT) break /* no schedule() */ /* q.pi_state->owner == current */ futex_private_hash_put() /* return from syscall */ rcuwait_wake_up(&q->requeue_wait) /* q is gone */ futex_requeue_pi_complete() publishes Q_REQUEUE_PI_LOCKED before calling rcuwait_wake_up(). The waiter observes this state in rcuwait_wait_event() before invoking schedule() in rcuwait_wait_event(). Here, the waiter is free leave the syscall before requeue task can complete the wake. To address this race skip rcuwait_wake_up() in the Q_REQUEUE_PI_LOCKED case. This state is only published by requeue_pi_wake_futex(), which saves q->task before futex_requeue_pi_complete() and wakes the waiter via wake_up_state(). This wake is intended to wake the waiter from its futex_do_wait() sleep. If the waiter is still sleeping there, it can not get into the Q_REQUEUE_PI_WAIT state (and require this removed wake). Should the waiter be woken up from futex_do_wait() by other means (as in this example) and sleep in futex_requeue_pi_wakeup_sync() then the wake_up_state() from requeue_pi_wake_futex() will wake it, too. Should the waiter task terminate before wake_up_state() had a chance to wake the task then the task pointer does not become invalid because the futex_hash_bucket::lock is held and the task pointer is RCU protected. [bigeasy: Updated comment and commit message]
Timeline
- CVE published
- Record last updated
Affected versions
- Linux Linux
From 07d91ef510fb16a2e0ca7453222105835b7ba3b8 · fixed in 220ee9e04ca3b7f014c000264aa6c884f036c86e; From 07d91ef510fb16a2e0ca7453222105835b7ba3b8 · fixed in 81aadbd09bf1dcd3238212f336ba699503557ae8; From 07d91ef510fb16a2e0ca7453222105835b7ba3b8 · fixed in 244f301759fd34b1dd0b4192ce44f8ef224e027d; From 07d91ef510fb16a2e0ca7453222105835b7ba3b8 · fixed in 7d1559126d86be6e4f6a85663dfbfe85caa47e37; From 07d91ef510fb16a2e0ca7453222105835b7ba3b8 · fixed in e4a4ccfa470f910b747b3ee8d18670ed8ac8a236; From 07d91ef510fb16a2e0ca7453222105835b7ba3b8 · fixed in a3b8d46fe401cba3a5c46dea610e6eb3dc15370e
- Linux Linux
5.15
- KernelLinux
From 5.15.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.110; From 6.13.0 · fixed in 6.18.51; From 6.19.0 · fixed in 7.2.5