# CVE-2026-74463: i2c: jz4780: Cache host clock rate at probe to prevent CCF prepare\_lock deadlock

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-08-15 · Updated: 2026-08-19

## Affected

- Linux: version range not reported
- Linux: 4.1

## Description

In the Linux kernel, the following vulnerability has been resolved: i2c: jz4780: Cache host clock rate at probe to prevent CCF prepare_lock deadlock Fix a severe AB/BA deadlock between the Common Clock Framework (CCF) and the I2C adapter lock, which triggers when an I2C-controlled clock generator client (like the Si5351) is registered or modified under the CCF. During an i2c client clock (generator) frequency change, the CCF acquires its global 'prepare_lock' mutex and the driver calls i2c_transfer() to update the client's chip registers, stalling for the adapter's I2C bus lock. Concurrently, an independent, parallel transfer on the same bus (e.g., a GPIO expander handling LEDs) can hold the I2C adapter lock. Inside this parallel transfer path, jz4780_i2c_set_speed() calls clk_get_rate() on the host controller's input clock to calculate bus timings. This call attempts to acquire the blocked CCF 'prepare_lock', creating a circular dependency that freezes the system. The jz4780 host controller clock itself is static and never changes at runtime. However, calling clk_get_rate() inside the active transfer path introduces an unnecessary dependency on the CCF internal locks. Eliminate this synchronous clk_get_rate() call from the active transfer path by caching the static host peripheral clock rate once - inside the private jz4780_i2c structure during jz4780_i2c_probe(). Update jz4780_i2c_set_speed() to use this cached value, safely decoupling active I2C transactions from the CCF internal locks without any risk of stale timings. Assisted-by web based Google AI (pinpointing the bug and writing the message).

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
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## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/cc111696ef420f6bb552b2526530067977f0b406
- https://git.kernel.org/stable/c/f96a719d9f8a797105ec5cacf568ab128e33391f
- https://git.kernel.org/stable/c/deffad5bb4f8b4f09e46252f24754ddc9960b244
- https://git.kernel.org/stable/c/14429dc1c756c35e106f01ff09cadccb82f5531d
- https://git.kernel.org/stable/c/b6cb47e186abba85a3b08aa3023067ab82577286
- https://git.kernel.org/stable/c/19b783335d62e7a2367436a6e1f1b37da1878360
- https://git.kernel.org/stable/c/aa1944b52d6492c48bdd17046578aa0d953546e6
- https://git.kernel.org/stable/c/d99607c888f26e8a4e9fe9772860cef4aff86bb4

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