CVE-2026-74463 i2c: jz4780: Cache host clock rate at probe to prevent CCF prepare_lock deadlock
A race condition in the JZ4780 I2C driver causes a system deadlock, leading to denial of service for local attackers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74463?
CVE-2026-74463 is a vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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).
Which versions are affected by CVE-2026-74463?
How do I fix CVE-2026-74463?
Apply the vendor's patch.
Is CVE-2026-74463 being exploited?
There is no known exploitation of CVE-2026-74463 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-74463, DEBIAN-CVE-2026-74463, GHSA-2xgc-rc56-qqm7, UBUNTU-CVE-2026-74463.