CVE-2026-43331

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> x86/kexec: Disable KCOV instrumentation after load_segments()<br /> <br /> The load_segments() function changes segment registers, invalidating GS base<br /> (which KCOV relies on for per-cpu data). When CONFIG_KCOV is enabled, any<br /> subsequent instrumented C code call (e.g. native_gdt_invalidate()) begins<br /> crashing the kernel in an endless loop.<br /> <br /> To reproduce the problem, it&amp;#39;s sufficient to do kexec on a KCOV-instrumented<br /> kernel:<br /> <br /> $ kexec -l /boot/otherKernel<br /> $ kexec -e<br /> <br /> The real-world context for this problem is enabling crash dump collection in<br /> syzkaller. For this, the tool loads a panic kernel before fuzzing and then<br /> calls makedumpfile after the panic. This workflow requires both CONFIG_KEXEC<br /> and CONFIG_KCOV to be enabled simultaneously.<br /> <br /> Adding safeguards directly to the KCOV fast-path (__sanitizer_cov_trace_pc())<br /> is also undesirable as it would introduce an extra performance overhead.<br /> <br /> Disabling instrumentation for the individual functions would be too fragile,<br /> so disable KCOV instrumentation for the entire machine_kexec_64.c and<br /> physaddr.c. If coverage-guided fuzzing ever needs these components in the<br /> future, other approaches should be considered.<br /> <br /> The problem is not relevant for 32 bit kernels as CONFIG_KCOV is not supported<br /> there.<br /> <br /> [ bp: Space out comment for better readability. ]