Описание
In the Linux kernel, the following vulnerability has been resolved:
futex: Fix private hash use-after-free on resize
poll_state_synchronize_rcu(mm->futex.phash.batches) is used by
futex_ref_drop() to check that a grace period has passed since the
current hash was published. This relies on batches referencing a grace
period which started after the hash pointer was assigned.
__futex_pivot_hash() sets mmph->batches before it replaces mmph->hash:
scoped_guard(rcu) {
mmph->batches = get_state_synchronize_rcu();
rcu_assign_pointer(mmph->hash, new);
}
The scoped_guard(rcu) doesn't stop new grace periods from starting, and
if one starts between those two assignments, futex_ref_drop() can move
forward while a reader still holds a pointer to the old hash.
Fix things by setting mmph->batches after assigning mmph->hash. The
scoped_guard(rcu) isn't needed, so let's drop that as well.
A flaw was found in the Linux kernel's futex (fast userspace mutex) subsystem. When resizing a private hash table, improper synchronization allows the old table memory to be released while another thread is still referencing it. A local attacker could exploit this race condition to trigger a use-after-free memory error, potentially resulting in privilege escalation or a denial of service (DoS) caused by a system crash.
Отчет
A race in private futex hash resizing can cause a use-after-free because the recorded RCU grace period may start before the new hash pointer is published. futex_ref_drop() may then conclude that the old hash is no longer used and allow it to be freed while a concurrent reader still holds a pointer to it. A local process using private futex operations may be able to trigger the vulnerable resize and race without administrative capabilities. For the CVSS the PR:L reflects that local user code execution is required but elevated system privileges are not normally required. AC:H applies because successful triggering depends on an RCU timing window during hash replacement and reference release. Impact is at least a local denial of service through a kernel crash. In the worst defensible case the confirmed use-after-free may permit broader memory corruption and privilege escalation if the released hash memory can be reused in a controllable way. The issue is not directly network reachable.
Меры по смягчению последствий
Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Fix deferred |
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Дополнительная информация
Статус:
4.7 Medium
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: futex: Fix private hash use-after-free on resize poll_state_synchronize_rcu(mm->futex.phash.batches) is used by futex_ref_drop() to check that a grace period has passed since the current hash was published. This relies on batches referencing a grace period which started after the hash pointer was assigned. __futex_pivot_hash() sets mmph->batches before it replaces mmph->hash: scoped_guard(rcu) { mmph->batches = get_state_synchronize_rcu(); rcu_assign_pointer(mmph->hash, new); } The scoped_guard(rcu) doesn't stop new grace periods from starting, and if one starts between those two assignments, futex_ref_drop() can move forward while a reader still holds a pointer to the old hash. Fix things by setting mmph->batches after assigning mmph->hash. The scoped_guard(rcu) isn't needed, so let's drop that as well.
In the Linux kernel, the following vulnerability has been resolved: futex: Fix private hash use-after-free on resize poll_state_synchronize_rcu(mm->futex.phash.batches) is used by futex_ref_drop() to check that a grace period has passed since the current hash was published. This relies on batches referencing a grace period which started after the hash pointer was assigned. __futex_pivot_hash() sets mmph->batches before it replaces mmph->hash: scoped_guard(rcu) { mmph->batches = get_state_synchronize_rcu(); rcu_assign_pointer(mmph->hash, new); } The scoped_guard(rcu) doesn't stop new grace periods from starting, and if one starts between those two assignments, futex_ref_drop() can move forward while a reader still holds a pointer to the old hash. Fix things by setting mmph->batches after assigning mmph->hash. The scoped_guard(rcu) isn't needed, so let's drop that as well.
In the Linux kernel, the following vulnerability has been resolved: f ...
In the Linux kernel, the following vulnerability has been resolved: futex: Fix private hash use-after-free on resize poll_state_synchronize_rcu(mm->futex.phash.batches) is used by futex_ref_drop() to check that a grace period has passed since the current hash was published. This relies on batches referencing a grace period which started after the hash pointer was assigned. __futex_pivot_hash() sets mmph->batches before it replaces mmph->hash: scoped_guard(rcu) { mmph->batches = get_state_synchronize_rcu(); rcu_assign_pointer(mmph->hash, new); } The scoped_guard(rcu) doesn't stop new grace periods from starting, and if one starts between those two assignments, futex_ref_drop() can move forward while a reader still holds a pointer to the old hash. Fix things by setting mmph->batches after assigning mmph->hash. The scoped_guard(rcu) isn't needed, so let's drop that as well.
4.7 Medium
CVSS3