CVE-2026-43331
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk2th percentile - higher than 2% of all known CVEs
Summary
A vulnerability has been identified in the Linux kernel related to the load_segments() function, which invalidates the GS base relied upon by KCOV. When CONFIG_KCOV is enabled, calls to instrumented C code can lead to kernel crashes in an endless loop.
Risk Assessment
This vulnerability may lead to system instability and kernel crashes, impacting service availability within the organization. It is particularly relevant in the context of crash dump collection in tools like syzkaller.
Recommendation
It is recommended to disable KCOV instrumentation in the machine_kexec_64.c and physaddr.c files to avoid crash issues. Other approaches should also be considered if there is a future need to use these components in fuzzing.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: x86/kexec: Disable KCOV instrumentation after load_segments() The load_segments() function changes segment registers, invalidating GS base (which KCOV relies on for per-cpu data). When CONFIG_KCOV is enabled, any subsequent instrumented C code call (e.g. native_gdt_invalidate()) begins crashing the kernel in an endless loop. To reproduce the problem, it's sufficient to do kexec on a KCOV-instrumented kernel: $ kexec -l /boot/otherKernel $ kexec -e The real-world context for this problem is enabling crash dump collection in syzkaller. For this, the tool loads a panic kernel before fuzzing and then calls makedumpfile after the panic. This workflow requires both CONFIG_KEXEC and CONFIG_KCOV to be enabled simultaneously. Adding safeguards directly to the KCOV fast-path (__sanitizer_cov_trace_pc()) is also undesirable as it would introduce an extra performance overhead. Disabling instrumentation for the individual functions would be too fragile, so disable KCOV instrumentation for the entire machine_kexec_64.c and physaddr.c. If coverage-guided fuzzing ever needs these components in the future, other approaches should be considered. The problem is not relevant for 32 bit kernels as CONFIG_KCOV is not supported there. [ bp: Space out comment for better readability. ]