selftests/bpf: convert test_dev_cgroup to test_progs

test_dev_cgroup is defined as a standalone test program, and so is not
executed in CI.

Convert it to test_progs framework so it is tested automatically in CI, and
remove the old test. In order to be able to run it in test_progs, /dev/null
must remain usable, so change the new test to test operations on devices
1:3 as valid, and operations on devices 1:5 (/dev/zero) as invalid.

Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
Link: https://lore.kernel.org/r/20240731-convert_dev_cgroup-v4-2-849425d90de6@bootlin.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

Author: Tropicao

tools/testing/selftests/bpf/.gitignore

@@ -9,7 +9,6 @@ test_lpm_map
 test_tag
 FEATURE-DUMP.libbpf
 fixdep
-test_dev_cgroup
 /test_progs
 /test_progs-no_alu32
 /test_progs-bpf_gcc

tools/testing/selftests/bpf/Makefile

@@ -67,7 +67,6 @@ endif
 
 # Order correspond to 'make run_tests' order
 TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test_progs \
-	test_dev_cgroup \
 	test_sock test_sockmap get_cgroup_id_user \
 	test_cgroup_storage \
 	test_tcpnotify_user test_sysctl \
@@ -292,7 +291,6 @@ JSON_WRITER		:= $(OUTPUT)/json_writer.o
 CAP_HELPERS	:= $(OUTPUT)/cap_helpers.o
 NETWORK_HELPERS := $(OUTPUT)/network_helpers.o
 
-$(OUTPUT)/test_dev_cgroup: $(CGROUP_HELPERS) $(TESTING_HELPERS)
 $(OUTPUT)/test_skb_cgroup_id_user: $(CGROUP_HELPERS) $(TESTING_HELPERS)
 $(OUTPUT)/test_sock: $(CGROUP_HELPERS) $(TESTING_HELPERS)
 $(OUTPUT)/test_sockmap: $(CGROUP_HELPERS) $(TESTING_HELPERS)

tools/testing/selftests/bpf/prog_tests/cgroup_dev.c

@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <sys/stat.h>
+#include <sys/sysmacros.h>
+#include <errno.h>
+#include "test_progs.h"
+#include "cgroup_helpers.h"
+#include "dev_cgroup.skel.h"
+
+#define TEST_CGROUP "/test-bpf-based-device-cgroup/"
+#define TEST_BUFFER_SIZE 64
+
+static void test_mknod(const char *path, mode_t mode, int dev_major,
+		       int dev_minor, int expected_ret, int expected_errno)
+{
+	int ret;
+
+	unlink(path);
+	ret = mknod(path, mode, makedev(dev_major, dev_minor));
+	ASSERT_EQ(ret, expected_ret, "mknod");
+	if (expected_ret)
+		ASSERT_EQ(errno, expected_errno, "mknod errno");
+	else
+		unlink(path);
+}
+
+static void test_read(const char *path, char *buf, int buf_size,
+		      int expected_ret, int expected_errno)
+{
+	int ret, fd;
+
+	fd = open(path, O_RDONLY);
+
+	/* A bare open on unauthorized device should fail */
+	if (expected_ret < 0) {
+		ASSERT_EQ(fd, expected_ret, "open ret for read");
+		ASSERT_EQ(errno, expected_errno, "open errno for read");
+		if (fd >= 0)
+			close(fd);
+		return;
+	}
+
+	if (!ASSERT_OK_FD(fd, "open ret for read"))
+		return;
+
+	ret = read(fd, buf, buf_size);
+	ASSERT_EQ(ret, expected_ret, "read");
+
+	close(fd);
+}
+
+static void test_write(const char *path, char *buf, int buf_size,
+		       int expected_ret, int expected_errno)
+{
+	int ret, fd;
+
+	fd = open(path, O_WRONLY);
+
+	/* A bare open on unauthorized device should fail */
+	if (expected_ret < 0) {
+		ASSERT_EQ(fd, expected_ret, "open ret for write");
+		ASSERT_EQ(errno, expected_errno, "open errno for write");
+		if (fd >= 0)
+			close(fd);
+		return;
+	}
+
+	if (!ASSERT_OK_FD(fd, "open ret for write"))
+		return;
+
+	ret = write(fd, buf, buf_size);
+	ASSERT_EQ(ret, expected_ret, "write");
+
+	close(fd);
+}
+
+void test_cgroup_dev(void)
+{
+	char buf[TEST_BUFFER_SIZE] = "some random test data";
+	struct dev_cgroup *skel;
+	int cgroup_fd;
+
+	cgroup_fd = cgroup_setup_and_join(TEST_CGROUP);
+	if (!ASSERT_OK_FD(cgroup_fd, "cgroup switch"))
+		return;
+
+	skel = dev_cgroup__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "load program"))
+		goto cleanup_cgroup;
+
+	skel->links.bpf_prog1 =
+		bpf_program__attach_cgroup(skel->progs.bpf_prog1, cgroup_fd);
+	if (!ASSERT_OK_PTR(skel->links.bpf_prog1, "attach_program"))
+		goto cleanup_progs;
+
+	if (test__start_subtest("allow-mknod"))
+		test_mknod("/dev/test_dev_cgroup_null", S_IFCHR, 1, 3, 0, 0);
+
+	if (test__start_subtest("allow-read"))
+		test_read("/dev/urandom", buf, TEST_BUFFER_SIZE,
+			  TEST_BUFFER_SIZE, 0);
+
+	if (test__start_subtest("allow-write"))
+		test_write("/dev/null", buf, TEST_BUFFER_SIZE,
+			   TEST_BUFFER_SIZE, 0);
+
+	if (test__start_subtest("deny-mknod"))
+		test_mknod("/dev/test_dev_cgroup_zero", S_IFCHR, 1, 5, -1,
+			   EPERM);
+
+	if (test__start_subtest("deny-read"))
+		test_read("/dev/random", buf, TEST_BUFFER_SIZE, -1, EPERM);
+
+	if (test__start_subtest("deny-write"))
+		test_write("/dev/zero", buf, TEST_BUFFER_SIZE, -1, EPERM);
+
+cleanup_progs:
+	dev_cgroup__destroy(skel);
+cleanup_cgroup:
+	cleanup_cgroup_environment();
+}