{"id":"CVE-2026-43331","summary":"x86/kexec: Disable KCOV instrumentation after load_segments()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nx86/kexec: Disable KCOV instrumentation after load_segments()\n\nThe load_segments() function changes segment registers, invalidating GS base\n(which KCOV relies on for per-cpu data). When CONFIG_KCOV is enabled, any\nsubsequent instrumented C code call (e.g. native_gdt_invalidate()) begins\ncrashing the kernel in an endless loop.\n\nTo reproduce the problem, it's sufficient to do kexec on a KCOV-instrumented\nkernel:\n\n  $ kexec -l /boot/otherKernel\n  $ kexec -e\n\nThe real-world context for this problem is enabling crash dump collection in\nsyzkaller. For this, the tool loads a panic kernel before fuzzing and then\ncalls makedumpfile after the panic. This workflow requires both CONFIG_KEXEC\nand CONFIG_KCOV to be enabled simultaneously.\n\nAdding safeguards directly to the KCOV fast-path (__sanitizer_cov_trace_pc())\nis also undesirable as it would introduce an extra performance overhead.\n\nDisabling instrumentation for the individual functions would be too fragile,\nso disable KCOV instrumentation for the entire machine_kexec_64.c and\nphysaddr.c. If coverage-guided fuzzing ever needs these components in the\nfuture, other approaches should be considered.\n\nThe problem is not relevant for 32 bit kernels as CONFIG_KCOV is not supported\nthere.\n\n  [ bp: Space out comment for better readability. ]","modified":"2026-07-15T01:48:54.901186573Z","published":"2026-05-08T13:31:18.787Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43331.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0e96cd314c0d819c1635d68125a4d77852c2162e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/1e3e98596c2769721ade0418434852fb3af4849a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/593d67032544b9271094fc9b43e437e017cb2b2f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/917e3ad3321e75ca0223d5ccf26ceda116aa51e1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/de05c66fab8847237a9ca216934e56d3ee837f08"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43331.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-43331"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"0d345996e4cb573f8cc81d49b3ee9a7fd2035bef"},{"fixed":"0e96cd314c0d819c1635d68125a4d77852c2162e"},{"fixed":"593d67032544b9271094fc9b43e437e017cb2b2f"},{"fixed":"1e3e98596c2769721ade0418434852fb3af4849a"},{"fixed":"de05c66fab8847237a9ca216934e56d3ee837f08"},{"fixed":"917e3ad3321e75ca0223d5ccf26ceda116aa51e1"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43331.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.6.0"},{"fixed":"6.6.143"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.93"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.22"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"6.19.12"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43331.json"}}],"schema_version":"1.7.5"}