static int check_call(struct bpf_verifier_env *env, int func_id, int insn_idx)
{
	const struct bpf_func_proto *fn = NULL;
	struct bpf_reg_state *regs;
	struct bpf_call_arg_meta meta;
	bool changes_data;
	int i, err;

	/* find function prototype */
	if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
		verbose(env, "invalid func %s#%d\n", func_id_name(func_id),
			func_id);
		return -EINVAL;
	}

	if (env->ops->get_func_proto)
		fn = env->ops->get_func_proto(func_id);

	if (!fn) {
		verbose(env, "unknown func %s#%d\n", func_id_name(func_id),
			func_id);
		return -EINVAL;
	}

	/* eBPF programs must be GPL compatible to use GPL-ed functions */
	if (!env->prog->gpl_compatible && fn->gpl_only) {
		verbose(env, "cannot call GPL only function from proprietary program\n");
		return -EINVAL;
	}

	/* With LD_ABS/IND some JITs save/restore skb from r1. */
	changes_data = bpf_helper_changes_pkt_data(fn->func);
	if (changes_data && fn->arg1_type != ARG_PTR_TO_CTX) {
		verbose(env, "kernel subsystem misconfigured func %s#%d: r1 != ctx\n",
			func_id_name(func_id), func_id);
		return -EINVAL;
	}

	memset(&meta, 0, sizeof(meta));
	meta.pkt_access = fn->pkt_access;

	/* We only support one arg being in raw mode at the moment, which
	 * is sufficient for the helper functions we have right now.
	 */
	err = check_raw_mode(fn);
	if (err) {
		verbose(env, "kernel subsystem misconfigured func %s#%d\n",
			func_id_name(func_id), func_id);
		return err;
	}

	/* check args */
	err = check_func_arg(env, BPF_REG_1, fn->arg1_type, &meta);
	if (err)
		return err;
	err = check_func_arg(env, BPF_REG_2, fn->arg2_type, &meta);
	if (err)
		return err;
	err = check_func_arg(env, BPF_REG_3, fn->arg3_type, &meta);
	if (err)
		return err;
	err = check_func_arg(env, BPF_REG_4, fn->arg4_type, &meta);
	if (err)
		return err;
	err = check_func_arg(env, BPF_REG_5, fn->arg5_type, &meta);
	if (err)
		return err;

	/* Mark slots with STACK_MISC in case of raw mode, stack offset
	 * is inferred from register state.
	 */
	for (i = 0; i < meta.access_size; i++) {
		err = check_mem_access(env, insn_idx, meta.regno, i, BPF_B, BPF_WRITE, -1);
		if (err)
			return err;
	}

	regs = cur_regs(env);
	/* reset caller saved regs */
	for (i = 0; i < CALLER_SAVED_REGS; i++) {
		mark_reg_not_init(env, regs, caller_saved[i]);
		check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
	}

	/* update return register (already marked as written above) */
	if (fn->ret_type == RET_INTEGER) {
		/* sets type to SCALAR_VALUE */
		mark_reg_unknown(env, regs, BPF_REG_0);
	} else if (fn->ret_type == RET_VOID) {
		regs[BPF_REG_0].type = NOT_INIT;
	} else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL) {
		struct bpf_insn_aux_data *insn_aux;

		regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
		/* There is no offset yet applied, variable or fixed */
		mark_reg_known_zero(env, regs, BPF_REG_0);
		regs[BPF_REG_0].off = 0;
		/* remember map_ptr, so that check_map_access()
		 * can check 'value_size' boundary of memory access
		 * to map element returned from bpf_map_lookup_elem()
		 */
		if (meta.map_ptr == NULL) {
			verbose(env,
				"kernel subsystem misconfigured verifier\n");
			return -EINVAL;
		}
		regs[BPF_REG_0].map_ptr = meta.map_ptr;
		regs[BPF_REG_0].id = ++env->id_gen;
		insn_aux = &env->insn_aux_data[insn_idx];
		if (!insn_aux->map_ptr)
			insn_aux->map_ptr = meta.map_ptr;
		else if (insn_aux->map_ptr != meta.map_ptr)
			insn_aux->map_ptr = BPF_MAP_PTR_POISON;
	} else {
		verbose(env, "unknown return type %d of func %s#%d\n",
			fn->ret_type, func_id_name(func_id), func_id);
		return -EINVAL;
	}

	err = check_map_func_compatibility(env, meta.map_ptr, func_id);
	if (err)
		return err;

	if (changes_data)
		clear_all_pkt_pointers(env);
	return 0;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.