linux/tools/testing/selftests/bpf/test_dev_cgroup.c

/* Copyright (c) 2017 Facebook
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <sys/time.h>
#include <sys/resource.h>

#include <linux/bpf.h>
#include <bpf/bpf.h>
#include <bpf/libbpf.h>

#include "cgroup_helpers.h"

#define DEV_CGROUP_PROG "./dev_cgroup.o"

#define TEST_CGROUP "test-bpf-based-device-cgroup/"

int main(int argc, char **argv)
{
	struct rlimit limit  = { RLIM_INFINITY, RLIM_INFINITY };
	struct bpf_object *obj;
	int error = EXIT_FAILURE;
	int prog_fd, cgroup_fd;
	__u32 prog_cnt;

	if (setrlimit(RLIMIT_MEMLOCK, &limit) < 0)
		perror("Unable to lift memlock rlimit");

	if (bpf_prog_load(DEV_CGROUP_PROG, BPF_PROG_TYPE_CGROUP_DEVICE,
			  &obj, &prog_fd)) {
		printf("Failed to load DEV_CGROUP program\n");
		goto out;
	}

	if (setup_cgroup_environment()) {
		printf("Failed to load DEV_CGROUP program\n");
		goto err;
	}

	/* Create a cgroup, get fd, and join it */
	cgroup_fd = create_and_get_cgroup(TEST_CGROUP);
	if (!cgroup_fd) {
		printf("Failed to create test cgroup\n");
		goto err;
	}

	if (join_cgroup(TEST_CGROUP)) {
		printf("Failed to join cgroup\n");
		goto err;
	}

	/* Attach bpf program */
	if (bpf_prog_attach(prog_fd, cgroup_fd, BPF_CGROUP_DEVICE, 0)) {
		printf("Failed to attach DEV_CGROUP program");
		goto err;
	}

	if (bpf_prog_query(cgroup_fd, BPF_CGROUP_DEVICE, 0, NULL, NULL,
			   &prog_cnt)) {
		printf("Failed to query attached programs");
		goto err;
	}

	/* All operations with /dev/zero and and /dev/urandom are allowed,
	 * everything else is forbidden.
	 */
	assert(system("rm -f /tmp/test_dev_cgroup_null") == 0);
	assert(system("mknod /tmp/test_dev_cgroup_null c 1 3"));
	assert(system("rm -f /tmp/test_dev_cgroup_null") == 0);

	/* /dev/zero is whitelisted */
	assert(system("rm -f /tmp/test_dev_cgroup_zero") == 0);
	assert(system("mknod /tmp/test_dev_cgroup_zero c 1 5") == 0);
	assert(system("rm -f /tmp/test_dev_cgroup_zero") == 0);

	assert(system("dd if=/dev/urandom of=/dev/zero count=64") == 0);

	/* src is allowed, target is forbidden */
	assert(system("dd if=/dev/urandom of=/dev/full count=64"));

	/* src is forbidden, target is allowed */
	assert(system("dd if=/dev/random of=/dev/zero count=64"));

	error = 0;
	printf("test_dev_cgroup:PASS\n");

err:
	cleanup_cgroup_environment();

out:
	return error;
}