Описание
In the Linux kernel, the following vulnerability has been resolved:
hwmon: (pwm-fan) Stop RPM timer before freeing tach data
sample_timer() rearms the RPM timer and accesses the devm-managed
ctx->tachs and ctx->pulses_per_revolution arrays. The cleanup action
which stops the timer is registered before those arrays are allocated.
Since devres releases entries in reverse order, driver detach can free
the arrays before pwm_fan_cleanup() shuts down the timer. A timer expiry
in that window accesses the freed tach data.
With a KASAN kernel, a test-only kprobe delayed entry to
pwm_fan_cleanup() while normal sysfs unbind ran. Each of three runs
reported three four-byte reads and two four-byte writes in sample_timer()
after its backing devm allocations had been freed. The helper did not
invoke the timer callback, cleanup actions or free functions.
With the fix, three matching unbind runs completed without KASAN, BUG,
WARNING, Oops or panic. Instrumentation confirmed that timer retirement
completed before the first timer backing allocation was released.
Split timer retirement from the power cleanup and register its devres
action after the timer backing data and IRQ actions are installed. This
preserves the early power rollback action while ensuring the timer is
retired before its backing data is released. Use timer_shutdown_sync()
because the callback can rearm itself.
A flaw was found in the Linux kernel's PWM fan driver. A local privileged user can cause a Denial of Service (DoS) or memory corruption by unbinding or detaching the driver. Due to an improper cleanup sequence, internal data structures are released while the sampling timer is still active, resulting in a use-after-free condition when the timer expires.
Отчет
A moderate-severity use-after-free flaw was found in the Linux kernel's PWM fan (hwmon pwm-fan) driver, affecting the Red Hat Enterprise Linux 9 and 10 kernels, Red Hat In-Vehicle OS 2, and OpenShift Container Platform releases built on RHEL CoreOS 9. The devres cleanup action that stops the RPM sampling timer is registered before the tachometer data arrays it protects are allocated; because devres releases resources in reverse registration order, unbinding or detaching the driver can free the ctx->tachs and ctx->pulses_per_revolution arrays while the self-rearming sample_timer() callback is still pending. A timer expiry in that window reads from and writes to the freed memory, which can result in kernel memory corruption or a crash and therefore a local denial of service. Exploitation requires local access with administrative privileges to initiate the driver unbind or detach and depends on winning a narrow timing race during teardown, which limits the practical risk. Red Hat Enterprise Linux 6, 7, and 8 (including kernel-rt) and OpenShift Container Platform releases built on RHEL CoreOS 8 are not affected because the vulnerable code is not present in those kernels. The fix is deferred to future planned kernel updates because the flaw is only triggerable by a privileged local user during driver teardown; the residual risk is a local kernel crash or memory corruption on systems using the pwm-fan driver with tachometer sampling enabled.
Меры по смягчению последствий
Mitigation for this issue is either not available or the currently available options do not 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 | ||
| Red Hat Enterprise Linux 6 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Fix deferred | ||
| Red Hat OpenShift Container Platform 4 | openshift/ose-rhel-coreos-8 | Not affected | ||
| Red Hat OpenShift Container Platform 4 | openshift/ose-rhel-coreos-9 | Fix deferred |
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Дополнительная информация
Статус:
EPSS
5.5 Medium
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: hwmon: (pwm-fan) Stop RPM timer before freeing tach data sample_timer() rearms the RPM timer and accesses the devm-managed ctx->tachs and ctx->pulses_per_revolution arrays. The cleanup action which stops the timer is registered before those arrays are allocated. Since devres releases entries in reverse order, driver detach can free the arrays before pwm_fan_cleanup() shuts down the timer. A timer expiry in that window accesses the freed tach data. With a KASAN kernel, a test-only kprobe delayed entry to pwm_fan_cleanup() while normal sysfs unbind ran. Each of three runs reported three four-byte reads and two four-byte writes in sample_timer() after its backing devm allocations had been freed. The helper did not invoke the timer callback, cleanup actions or free functions. With the fix, three matching unbind runs completed without KASAN, BUG, WARNING, Oops or panic. Instrumentation confirmed that timer retirement com...
In the Linux kernel, the following vulnerability has been resolved: hwmon: (pwm-fan) Stop RPM timer before freeing tach data sample_timer() rearms the RPM timer and accesses the devm-managed ctx->tachs and ctx->pulses_per_revolution arrays. The cleanup action which stops the timer is registered before those arrays are allocated. Since devres releases entries in reverse order, driver detach can free the arrays before pwm_fan_cleanup() shuts down the timer. A timer expiry in that window accesses the freed tach data. With a KASAN kernel, a test-only kprobe delayed entry to pwm_fan_cleanup() while normal sysfs unbind ran. Each of three runs reported three four-byte reads and two four-byte writes in sample_timer() after its backing devm allocations had been freed. The helper did not invoke the timer callback, cleanup actions or free functions. With the fix, three matching unbind runs completed without KASAN, BUG, WARNING, Oops or panic. Instrumentation confirmed that timer retirement c
In the Linux kernel, the following vulnerability has been resolved: h ...
In the Linux kernel, the following vulnerability has been resolved: hwmon: (pwm-fan) Stop RPM timer before freeing tach data sample_timer() rearms the RPM timer and accesses the devm-managed ctx->tachs and ctx->pulses_per_revolution arrays. The cleanup action which stops the timer is registered before those arrays are allocated. Since devres releases entries in reverse order, driver detach can free the arrays before pwm_fan_cleanup() shuts down the timer. A timer expiry in that window accesses the freed tach data. With a KASAN kernel, a test-only kprobe delayed entry to pwm_fan_cleanup() while normal sysfs unbind ran. Each of three runs reported three four-byte reads and two four-byte writes in sample_timer() after its backing devm allocations had been freed. The helper did not invoke the timer callback, cleanup actions or free functions. With the fix, three matching unbind runs completed without KASAN, BUG, WARNING, Oops or panic. Instrumentation confirmed that timer retiremen...
EPSS
5.5 Medium
CVSS3