In the Linux kernel, the following vulnerability has been resolved: bpf: Check the helper function is valid in gethelperproto kernel test robot reported verifier bug [1] where the helper func pointer could be NULL due to disabled config option. As Alexei suggested we could check on that in gethelperproto directly. Marking tailcall helper func with BPFPTR_POISON, because it is unused by design. [1] https://lore.kernel.org/oe-lkp/202507160818.68358831-lkp@intel.com