static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
				int access_size, bool zero_size_allowed,
				struct bpf_call_arg_meta *meta)
{
	struct bpf_verifier_state *state = env->cur_state;
	struct bpf_reg_state *regs = state->regs;
	int off, i, slot, spi;

	if (regs[regno].type != PTR_TO_STACK) {
		/* Allow zero-byte read from NULL, regardless of pointer type */
		if (zero_size_allowed && access_size == 0 &&
		    register_is_null(regs[regno]))
			return 0;

		verbose(env, "R%d type=%s expected=%s\n", regno,
			reg_type_str[regs[regno].type],
			reg_type_str[PTR_TO_STACK]);
		return -EACCES;
	}

	/* Only allow fixed-offset stack reads */
	if (!tnum_is_const(regs[regno].var_off)) {
		char tn_buf[48];

 		tnum_strn(tn_buf, sizeof(tn_buf), regs[regno].var_off);
 		verbose(env, "invalid variable stack read R%d var_off=%s\n",
 			regno, tn_buf);
		return -EACCES;
 	}
 	off = regs[regno].off + regs[regno].var_off.value;
 	if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||
	    access_size < 0 || (access_size == 0 && !zero_size_allowed)) {
		verbose(env, "invalid stack type R%d off=%d access_size=%d\n",
			regno, off, access_size);
		return -EACCES;
	}

	if (env->prog->aux->stack_depth < -off)
		env->prog->aux->stack_depth = -off;

	if (meta && meta->raw_mode) {
		meta->access_size = access_size;
		meta->regno = regno;
		return 0;
	}

	for (i = 0; i < access_size; i++) {
		slot = -(off + i) - 1;
		spi = slot / BPF_REG_SIZE;
		if (state->allocated_stack <= slot ||
		    state->stack[spi].slot_type[slot % BPF_REG_SIZE] !=
			STACK_MISC) {
			verbose(env, "invalid indirect read from stack off %d+%d size %d\n",
				off, i, access_size);
			return -EACCES;
		}
	}
	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.