Linux Kernel KCOV Instrumentation Disabling Vulnerability in KEXEC Context

A vulnerability exists in the Linux kernel's handling of KCOV (kernel coverage) instrumentation during KEXEC (kernel execution) operations on x86 architectures. When both CONFIG_KCOV and CONFIG_KEXEC are enabled, the load_segments() function disrupts the GS base, which KCOV relies on for per-CPU data. This disruption causes subsequent instrumented C code calls to crash the kernel in an infinite loop. The issue does not affect 32-bit kernels, as they do not support KCOV.

Impact

The vulnerability leads to a kernel crash, causing a denial of service by creating an endless loop of crashes.

Reproduction

To reproduce this vulnerability, load a kernel with KCOV instrumentation using the KEXEC command, then execute the KEXEC operation. This will trigger the crash loop due to the disrupted GS base.

Remediation

The vulnerability has been addressed by modifying the KCOV instrumentation settings in the Linux kernel's x86 architecture files. Users should apply the latest patches available in the Linux kernel stable tree to mitigate this issue.