Linux Kernel Clang kCFI Vulnerability in ext4 Module Unloading

A vulnerability in the Linux kernel's ext4 file system module can lead to a runtime failure when the module is unloaded. This issue arises from a function prototype mismatch that Clang's kernel control flow integrity (kCFI) feature, enabled with CONFIG_CFI_CLANG, detects. The mismatch can cause a kernel panic or terminate a thread, creating a potential denial-of-service scenario. The vulnerability affects several Linux kernel versions in the stable branch.

Impact

Exploitation of this vulnerability causes a kernel panic or terminates the thread, disrupting system operations and potentially leading to a denial-of-service condition.

Reproduction

To reproduce this vulnerability, load the ext4 file system module with Clang's kernel control flow integrity feature enabled. Once the module is loaded, unload it. The improper function prototype for the 'release' handler will trigger a kCFI validation failure, causing a kernel panic or terminating the thread.

Remediation

Users can upgrade to the latest patched version of the Linux kernel where this vulnerability has been addressed.