CVE-2026-31741

Summary

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

counter: rz-mtu3-cnt: prevent counter from being toggled multiple times

Runtime PM counter is incremented / decremented each time the sysfs enable file is written to.

If user writes 0 to the sysfs enable file multiple times, runtime PM usage count underflows, generating the following message.

rz-mtu3-counter rz-mtu3-counter.0: Runtime PM usage count underflow!

At the same time, hardware registers end up being accessed with clocks off in rz_mtu3_terminate_counter() to disable an already disabled channel.

If user writes 1 to the sysfs enable file multiple times, runtime PM usage count will be incremented each time, requiring the same number of 0 writes to get it back to 0.

If user writes 0 to the sysfs enable file while PWM is in progress, PWM is stopped without counter being the owner of the underlying MTU3 channel.

Check against the cached count_is_enabled value and exit if the user is trying to set the same enable value.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/885aa739a07ab45e90dfa997205acec97979ce4e
• https://git.kernel.org/stable/c/ced8b48420eddb1251f93c22dc23fa136490b3cd
• https://git.kernel.org/stable/c/e07237df8538b0ae98dce112e4f6db093d767f80
• https://git.kernel.org/stable/c/f5f6f06d7e6d262026578b59ba7426eb04acce5d
• https://git.kernel.org/stable/c/67c3f99bed6f422ba343d2b70a2eeeccdfd91bef

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