CVE-2023-52928 bpf: Skip invalid kfunc call in backtrack_insn

In the Linux kernel, the following vulnerability has been resolved: bpf: Skip invalid kfunc call in backtrackinsn The verifier skips invalid kfunc call in checkkfunccall, which would be captured in fixupkfunccall if such insn is not eliminated by dead code elimination. However, this can lead to t...