Linux Kernel PowerPC Code Patching Vulnerability Allows User Memory Access KASAN Report

A vulnerability in the Linux kernel's handling of PowerPC code patching has been identified. This issue arises because the kernel's AddressSanitizer (KASAN) does not report user-memory-access errors during the instruction patching process, potentially leading to undetected memory access violations. The vulnerability was observed on a Talos II (Power9) system running kernel version 6.13, where KASAN reported a user-memory-access error related to the 'systemd' process. The issue stems from a recent change in how the kernel patches instructions, which inadvertently exposed a user-space memory access violation that KASAN failed to catch.

Impact

Exploitation of this vulnerability could lead to unreported user-memory-access violations, allowing for potential memory corruption or unauthorized access to user-space memory from kernel-space processes.