CVE-2026-98626

In the Linux kernel, the following vulnerability has been resolved:

bpf: Restrict CO-RE poisoning to relocatable instructions

CO-RE relocation records can name any instruction offset. When a relocation cannot be resolved, bpf core patch insn() currently poisons its target before checking whether that instruction is a valid relocation target. Malformed metadata can therefore replace jumps, calls, exits, register-source arithmetic, or non-immediate loads instead of failing at the relocation step.

Handle poisoning only after the instruction has passed the same class and operand-form checks used for a resolved relocation. Route invalid forms through the existing diagnostic and return a hard error. Keep poisoning supported instructions, including both halves of a plain ldimm64, so an unresolved relocation in dead code remains valid.

Extend bpf core poison insn() to poison both halves of ldimm64, and return its status directly from each validated instruction case. This avoids routing the success path through a common label and leaves the helper free to report errors.

The shared relocation code applies this restriction to both libbpf and in-kernel CO-RE.