CVE-2026-99248
Received Received - Intake

Runtime PM Clk WARN Flood in Linux Kernel i2c-xiic

Vulnerability report for CVE-2026-99248, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.

Publication date: 2026-11-03

Last updated on: 2026-11-03

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: i2c: xiic: restore non-managed runtime PM to fix clk WARN flood The devres conversion replaced manual pm_runtime_enable()/disable() with devm_pm_runtime_set_active_enabled() and dropped the remove-time runtime PM teardown. The managed release tears runtime PM down in the wrong order: it calls pm_runtime_dont_use_autosuspend() before pm_runtime_disable(), i.e. while runtime PM is still enabled, and devres is LIFO so the devm_clk_get_enabled() release runs afterwards. At remove(), pm_runtime_put_sync() leaves the device active with the autosuspend timer armed. Clearing use_autosuspend then makes rpm_idle() suspend immediately, and xiic_i2c_runtime_suspend() clk_disable()s the clock. The later devm_clk_get_enabled() release clk_disable_unprepare()s the already-disabled clock, so clk_core_disable() WARNs ("clkN already disabled") on every teardown. Drop the managed helper and restore the non-managed runtime PM setup and teardown, so runtime PM is enabled once in probe and disabled once in remove and the clock enable count stays balanced. Order the remove teardown so runtime PM is disabled before the usage count is dropped: pm_runtime_disable() followed by pm_runtime_put_noidle() instead of pm_runtime_put_sync(). Dropping the count first with autosuspend still enabled arms the autosuspend timer, and a preemption before pm_runtime_disable() lets it expire, suspend the device and clk_disable() the clock, which the devm release then disables again - the same WARN. Restore the non-managed IRQ request as well. The probe error paths now unwind runtime PM by hand via goto, and a devm-registered handler is only freed later during devres unwind, so it would stay live across the manual teardown (and across any future failing step added after it). Request the IRQ with request_threaded_irq() and free it explicitly in the probe error path and in remove. The probe error path also clears use_autosuspend, to match the teardown in remove().

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Meta Information

Published
2026-11-03
Last Modified
2026-11-03
Generated
2026-11-03
AI Q&A
2026-11-03
EPSS Evaluated
N/A
NVD
EUVD

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
Linux Linux 50c63491ff267f2860a6d8cb70c9a30ab701b9d3
Linux Linux 50c63491ff267f2860a6d8cb70c9a30ab701b9d3
Linux Linux 7.1

Helpful Resources

Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves incorrect handling of runtime power management (PM) for the I2C controller (xiic). The issue stems from replacing manual PM control with a managed devres helper, which disrupts the proper order of operations during device removal. This causes the clock to be disabled twice, triggering a warning about an already-disabled clock.

Detection Guidance

This vulnerability is specific to the Linux kernel's i2c-xiic driver and requires kernel-level inspection. Detection involves checking the kernel version and driver state. Use commands like 'uname -a' to verify kernel version and 'lsmod | grep xiic' to check if the vulnerable driver is loaded.

Impact Analysis

The vulnerability may cause kernel warnings during device teardown, particularly when removing the I2C controller driver. These warnings indicate a clock disable mismatch but do not directly affect functionality or security. However, repeated warnings could clutter system logs and indicate improper resource management.

Mitigation Strategies

Apply a kernel update that includes the fix for this issue. If an update is not available, disable the xiic driver module if not in use. Monitor kernel logs for 'clkN already disabled' warnings which indicate the issue.

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