CVE-2026-43227 — clocksource/drivers/sh_tmu: Always leave device running after probe

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

clocksource/drivers/sh_tmu: Always leave device running after probe

The TMU device can be used as both a clocksource and a clockevent provider. The driver tries to be smart and power itself on and off, as well as enabling and disabling its clock when it's not in operation. This behavior is slightly altered if the TMU is used as an early platform device in which case the device is left powered on after probe, but the clock is still enabled and disabled at runtime.

This has worked for a long time, but recent improvements in PREEMPT_RT and PROVE_LOCKING have highlighted an issue. As the TMU registers itself as a clockevent provider, clockevents_register_device(), it needs to use raw spinlocks internally as this is the context of which the clockevent framework interacts with the TMU driver. However in the context of holding a raw spinlock the TMU driver can't really manage its power state or clock with calls to pm_runtime_*() and clk_*() as these calls end up in other platform drivers using regular spinlocks to control power and clocks.

This mix of spinlock contexts trips a lockdep warning.

============================= [ BUG: Invalid wait context ] 6.18.0-arm64-renesas-09926-gee959e7c5e34 #1 Not tainted ----------------------------- swapper/0/0 is trying to lock: ffff000008c9e180 (&dev->power.lock){-...}-{3:3}, at: __pm_runtime_resume+0x38/0x88 other info that might help us debu…

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CVE-2026-43227 — clocksource/drivers/sh_tmu: Always leave device running after probe