CVE-2026-63825: gcov: use atomic counter updates to fix concurrent access crashes

Affected Software

Remediation

Recommended actions to resolve this vulnerability, in priority order.

1. Configuration

   Adjust the kernel build Makefiles so the CFLAGS_GCOV block is moved from its original position (before the arch Makefile include) to after the core KBUILD_CFLAGS assignments but before the arch KBUILD_CFLAGS include; this ensures the GCOV optimization uses atomic counter updates to prevent concurrent access crashes.

   Linux kernel build (KBUILD_CFLAGS / scripts/Makefile.gcc-plugins) CFLAGS_GCOV block placement = Move the CFLAGS_GCOV block to after the core KBUILD_CFLAGS assignments but before include of arch-specific KBUILD_CFLAGS (per patch description)
2. Configuration

   Enable GCOV atomic counter updates by adding -fprofile-update=prefer-atomic to CFLAGS_GCOV at the global level (as described), while avoiding GCC plugin flags (-fplugin=) and omitting the flag on architectures where it would introduce libatomic dependencies (e.g., outline-atomics on arm64).

   Linux kernel build (GCOV instrumentation) -fprofile-update=prefer-atomic in CFLAGS_GCOV = enabled conditionally (x86_64, arm64, s390, etc. as described)

Event History

Frequently Asked Questions