Linux Kernel MIPS CPU Info Runtime Warning Vulnerability

A vulnerability in the Linux kernel's MIPS architecture has been addressed. When both CONFIG_CPUMASK_OFFSTACK and CONFIG_DEBUG_PER_CPU_MAPS are enabled, the 'cpu_max_bits_warn()' function triggers a runtime warning while '/proc/cpuinfo' is being displayed. This issue arises because the function iterates over CPUs using the constant 'NR_CPUS' instead of the runtime limit 'nr_cpu_ids'. The warning can be seen in the kernel log, indicating the source of the problem and the hardware details.

Impact

The vulnerability causes a misleading runtime warning that could obscure other important messages in the system log.

Reproduction

To reproduce this vulnerability, compile the Linux kernel with the MIPS architecture, enabling both CONFIG_CPUMASK_OFFSTACK and CONFIG_DEBUG_PER_CPU_MAPS. After booting the kernel, the warning will be generated when '/proc/cpuinfo' is accessed, indicating that the 'cpu_max_bits_warn()' function has encountered an issue by using the incorrect CPU iteration limit.

Remediation

The vulnerability has been fixed in the official Linux kernel repository. Users should upgrade to the latest version.