Linux Kernel i2c PIIX4 Adapter Resource Leak Vulnerability

A vulnerability in the Linux kernel's i2c subsystem related to the PIIX4 adapter can lead to a resource leak. When the PIIX4 adapter is probed, it is registered without properly setting the adapter count, which defaults to zero. This oversight causes the adapter not to be removed when the module is unloaded, leading to leaked resources such as the i2c client and device. These leaked resources can be accessed by the i2c or bus systems, potentially causing issues, such as a page fault error when the freed resources are accessed.

Impact

The vulnerability causes a resource leak by failing to remove the PIIX4 i2c adapter when the module is unloaded. This leak can lead to accessing freed resources, causing kernel page fault errors.

Reproduction

The vulnerability can be reproduced by loading the i2c_piix4 module, which registers a PIIX4 adapter with an incorrect count. When the module is removed, the adapter is not deleted, leading to a resource leak. This leak can be observed by reloading the module, which will trigger a page fault error due to the accessed freed resources.

Remediation

The issue can be fixed by correctly setting the adapter count to 1 for the PIIX4 adapter, ensuring it is properly removed when the module is unloaded.