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.
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.
Metrics
Affected Vendors & Products
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Tue, 06 Oct 2026 09:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | hwmon: (pwm-fan) Stop RPM timer before freeing tach data | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
Sign in to view the affected projects.
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-10-06T08:44:36.944Z
Reserved: 2026-09-25T10:25:14.324Z
Link: CVE-2026-98198
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-10-06T09:18:05.440
Modified: 2026-10-06T09:18:05.440
Link: CVE-2026-98198
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.