selftests/bpf: add a test for device cgroup controller

Add a test for device cgroup controller.

The test loads a simple bpf program which logs all
device access attempts using trace_printk() and forbids
all operations except operations with /dev/zero and
/dev/urandom.

Then the test creates and joins a test cgroup, and attaches
the bpf program to it.

Then it tries to perform some simple device operations
and checks the result:

  create /dev/null (should fail)
  create /dev/zero (should pass)
  copy data from /dev/urandom to /dev/zero (should pass)
  copy data from /dev/urandom to /dev/full (should fail)
  copy data from /dev/random to /dev/zero (should fail)

Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 93 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/test_dev_cgroup.c b/tools/testing/selftests/bpf/test_dev_cgroup.c
new file mode 100644
index 000000000000..02c85d6c89b0
--- /dev/null
+++ b/tools/testing/selftests/bpf/test_dev_cgroup.c
@@ -0,0 +1,93 @@
+/* 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 <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 bpf_object *obj;
+	int error = EXIT_FAILURE;
+	int prog_fd, cgroup_fd;
+	__u32 prog_cnt;
+
+	if (bpf_prog_load(DEV_CGROUP_PROG, BPF_PROG_TYPE_CGROUP_DEVICE,
+			  &obj, &prog_fd)) {
+		printf("Failed to load DEV_CGROUP program\n");
+		goto err;
+	}
+
+	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();
+
+	return error;
+}