bpf: reject negative CO-RE accessor indices in bpf_core_parse_spec()

...

CVE-2026-45839

In the Linux kernel, the following vulnerability has been resolved: bpf: reject negative CO-RE accessor indices in bpfcoreparsespec CO-RE accessor strings are colon-separated indices that describe a path from a root BTF type to a target field, e.g. "0:1:2" walks through nested struct members...