Linux Kernel PowerPC64 Ftrace Livepatching R15 Clobber Vulnerability

A vulnerability in the Linux kernel's PowerPC64 ftrace implementation has been addressed. The issue arose because the r15 register, which is always clobbered when using PPC_FTRACE_OUT_OF_LINE, was not properly restored during livepatching. This oversight led to kernel data access errors, as the clobbered r15 was not available when needed, causing faults in the kernel's operation.

Impact

The vulnerability could lead to kernel crashes or data access violations, as the clobbered r15 register was not restored during livepatching, causing the kernel to access invalid memory areas.

Reproduction

The vulnerability can be reproduced by applying a livepatch that does not account for the r15 register being clobbered. This can be done by creating a livepatch that modifies kernel behavior without restoring r15, which will then lead to a kernel data access error when the modified behavior is executed.

Remediation

Users should apply the latest patches from the Linux kernel stable branch, where this vulnerability has been addressed.