x86/kexec: Disable KCOV instrumentation after load_segments()

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Summary

CVECVE-2026-43331
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-08 14:16:42 UTC
Updated2026-05-08 14:16:42 UTC
DescriptionIn 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. ]

Risk And Classification

EPSS: 0.000170000 probability, percentile 0.041290000 (date 2026-05-11)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef 1e3e98596c2769721ade0418434852fb3af4849a git Not specified
CNA Linux Linux affected 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef de05c66fab8847237a9ca216934e56d3ee837f08 git Not specified
CNA Linux Linux affected 0d345996e4cb573f8cc81d49b3ee9a7fd2035bef 917e3ad3321e75ca0223d5ccf26ceda116aa51e1 git Not specified
CNA Linux Linux affected 6.6 Not specified
CNA Linux Linux unaffected 6.6 semver Not specified
CNA Linux Linux unaffected 6.18.22 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.12 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/de05c66fab8847237a9ca216934e56d3ee837f08 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/917e3ad3321e75ca0223d5ccf26ceda116aa51e1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1e3e98596c2769721ade0418434852fb3af4849a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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