selftests/bpf: Add tests for fd_array_cnt

Add a new set of tests to test the new field in PROG_LOAD-related
part of bpf_attr: fd_array_cnt.

Add the following test cases:

* fd_array_cnt/no-fd-array: program is loaded in a normal
way, without any fd_array present

* fd_array_cnt/fd-array-ok: pass two extra non-used maps,
check that they're bound to the program

* fd_array_cnt/fd-array-dup-input: pass a few extra maps,
only two of which are unique

* fd_array_cnt/fd-array-ref-maps-in-array: pass a map in
fd_array which is also referenced from within the program

* fd_array_cnt/fd-array-trash-input: pass array with some trash

* fd_array_cnt/fd-array-2big: pass too large array

All the tests above are using the bpf(2) syscall directly,
no libbpf involved.

Signed-off-by: Anton Protopopov <[e-mail]>
Signed-off-by: Andrii Nakryiko <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

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

···
+// SPDX-License-Identifier: GPL-2.0
+
+#include <test_progs.h>
+
+#include <linux/btf.h>
+#include <bpf/bpf.h>
+
+#include "../test_btf.h"
+
+static inline int new_map(void)
+{
+	const char *name = NULL;
+	__u32 max_entries = 1;
+	__u32 value_size = 8;
+	__u32 key_size = 4;
+
+	return bpf_map_create(BPF_MAP_TYPE_ARRAY, name,
+			      key_size, value_size,
+			      max_entries, NULL);
+}
+
+static int new_btf(void)
+{
+	struct btf_blob {
+		struct btf_header btf_hdr;
+		__u32 types[8];
+		__u32 str;
+	} raw_btf = {
+		.btf_hdr = {
+			.magic = BTF_MAGIC,
+			.version = BTF_VERSION,
+			.hdr_len = sizeof(struct btf_header),
+			.type_len = sizeof(raw_btf.types),
+			.str_off = offsetof(struct btf_blob, str) - offsetof(struct btf_blob, types),
+			.str_len = sizeof(raw_btf.str),
+		},
+		.types = {
+			/* long */
+			BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 64, 8),  /* [1] */
+			/* unsigned long */
+			BTF_TYPE_INT_ENC(0, 0, 0, 64, 8),  /* [2] */
+		},
+	};
+
+	return bpf_btf_load(&raw_btf, sizeof(raw_btf), NULL);
+}
+
+#define Close(FD) do {		\
+	if ((FD) >= 0) {	\
+		close(FD);	\
+		FD = -1;	\
+	}			\
+} while(0)
+
+static bool map_exists(__u32 id)
+{
+	int fd;
+
+	fd = bpf_map_get_fd_by_id(id);
+	if (fd >= 0) {
+		close(fd);
+		return true;
+	}
+	return false;
+}
+
+static bool btf_exists(__u32 id)
+{
+	int fd;
+
+	fd = bpf_btf_get_fd_by_id(id);
+	if (fd >= 0) {
+		close(fd);
+		return true;
+	}
+	return false;
+}
+
+static inline int bpf_prog_get_map_ids(int prog_fd, __u32 *nr_map_ids, __u32 *map_ids)
+{
+	__u32 len = sizeof(struct bpf_prog_info);
+	struct bpf_prog_info info;
+	int err;
+
+	memset(&info, 0, len);
+	info.nr_map_ids = *nr_map_ids,
+	info.map_ids = ptr_to_u64(map_ids),
+
+	err = bpf_prog_get_info_by_fd(prog_fd, &info, &len);
+	if (!ASSERT_OK(err, "bpf_prog_get_info_by_fd"))
+		return -1;
+
+	*nr_map_ids = info.nr_map_ids;
+
+	return 0;
+}
+
+static int __load_test_prog(int map_fd, const int *fd_array, int fd_array_cnt)
+{
+	/* A trivial program which uses one map */
+	struct bpf_insn insns[] = {
+		BPF_LD_MAP_FD(BPF_REG_1, map_fd),
+		BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	LIBBPF_OPTS(bpf_prog_load_opts, opts);
+
+	opts.fd_array = fd_array;
+	opts.fd_array_cnt = fd_array_cnt;
+
+	return bpf_prog_load(BPF_PROG_TYPE_XDP, NULL, "GPL", insns, ARRAY_SIZE(insns), &opts);
+}
+
+static int load_test_prog(const int *fd_array, int fd_array_cnt)
+{
+	int map_fd;
+	int ret;
+
+	map_fd = new_map();
+	if (!ASSERT_GE(map_fd, 0, "new_map"))
+		return map_fd;
+
+	ret = __load_test_prog(map_fd, fd_array, fd_array_cnt);
+	close(map_fd);
+	return ret;
+}
+
+static bool check_expected_map_ids(int prog_fd, int expected, __u32 *map_ids, __u32 *nr_map_ids)
+{
+	int err;
+
+	err = bpf_prog_get_map_ids(prog_fd, nr_map_ids, map_ids);
+	if (!ASSERT_OK(err, "bpf_prog_get_map_ids"))
+		return false;
+	if (!ASSERT_EQ(*nr_map_ids, expected, "unexpected nr_map_ids"))
+		return false;
+
+	return true;
+}
+
+/*
+ * Load a program, which uses one map. No fd_array maps are present.
+ * On return only one map is expected to be bound to prog.
+ */
+static void check_fd_array_cnt__no_fd_array(void)
+{
+	__u32 map_ids[16];
+	__u32 nr_map_ids;
+	int prog_fd = -1;
+
+	prog_fd = load_test_prog(NULL, 0);
+	if (!ASSERT_GE(prog_fd, 0, "BPF_PROG_LOAD"))
+		return;
+	nr_map_ids = ARRAY_SIZE(map_ids);
+	check_expected_map_ids(prog_fd, 1, map_ids, &nr_map_ids);
+	close(prog_fd);
+}
+
+/*
+ * Load a program, which uses one map, and pass two extra, non-equal, maps in
+ * fd_array with fd_array_cnt=2. On return three maps are expected to be bound
+ * to the program.
+ */
+static void check_fd_array_cnt__fd_array_ok(void)
+{
+	int extra_fds[2] = { -1, -1 };
+	__u32 map_ids[16];
+	__u32 nr_map_ids;
+	int prog_fd = -1;
+
+	extra_fds[0] = new_map();
+	if (!ASSERT_GE(extra_fds[0], 0, "new_map"))
+		goto cleanup;
+	extra_fds[1] = new_map();
+	if (!ASSERT_GE(extra_fds[1], 0, "new_map"))
+		goto cleanup;
+	prog_fd = load_test_prog(extra_fds, 2);
+	if (!ASSERT_GE(prog_fd, 0, "BPF_PROG_LOAD"))
+		goto cleanup;
+	nr_map_ids = ARRAY_SIZE(map_ids);
+	if (!check_expected_map_ids(prog_fd, 3, map_ids, &nr_map_ids))
+		goto cleanup;
+
+	/* maps should still exist when original file descriptors are closed */
+	Close(extra_fds[0]);
+	Close(extra_fds[1]);
+	if (!ASSERT_EQ(map_exists(map_ids[0]), true, "map_ids[0] should exist"))
+		goto cleanup;
+	if (!ASSERT_EQ(map_exists(map_ids[1]), true, "map_ids[1] should exist"))
+		goto cleanup;
+
+	/* some fds might be invalid, so ignore return codes */
+cleanup:
+	Close(extra_fds[1]);
+	Close(extra_fds[0]);
+	Close(prog_fd);
+}
+
+/*
+ * Load a program with a few extra maps duplicated in the fd_array.
+ * After the load maps should only be referenced once.
+ */
+static void check_fd_array_cnt__duplicated_maps(void)
+{
+	int extra_fds[4] = { -1, -1, -1, -1 };
+	__u32 map_ids[16];
+	__u32 nr_map_ids;
+	int prog_fd = -1;
+
+	extra_fds[0] = extra_fds[2] = new_map();
+	if (!ASSERT_GE(extra_fds[0], 0, "new_map"))
+		goto cleanup;
+	extra_fds[1] = extra_fds[3] = new_map();
+	if (!ASSERT_GE(extra_fds[1], 0, "new_map"))
+		goto cleanup;
+	prog_fd = load_test_prog(extra_fds, 4);
+	if (!ASSERT_GE(prog_fd, 0, "BPF_PROG_LOAD"))
+		goto cleanup;
+	nr_map_ids = ARRAY_SIZE(map_ids);
+	if (!check_expected_map_ids(prog_fd, 3, map_ids, &nr_map_ids))
+		goto cleanup;
+
+	/* maps should still exist when original file descriptors are closed */
+	Close(extra_fds[0]);
+	Close(extra_fds[1]);
+	if (!ASSERT_EQ(map_exists(map_ids[0]), true, "map should exist"))
+		goto cleanup;
+	if (!ASSERT_EQ(map_exists(map_ids[1]), true, "map should exist"))
+		goto cleanup;
+
+	/* some fds might be invalid, so ignore return codes */
+cleanup:
+	Close(extra_fds[1]);
+	Close(extra_fds[0]);
+	Close(prog_fd);
+}
+
+/*
+ * Check that if maps which are referenced by a program are
+ * passed in fd_array, then they will be referenced only once
+ */
+static void check_fd_array_cnt__referenced_maps_in_fd_array(void)
+{
+	int extra_fds[1] = { -1 };
+	__u32 map_ids[16];
+	__u32 nr_map_ids;
+	int prog_fd = -1;
+
+	extra_fds[0] = new_map();
+	if (!ASSERT_GE(extra_fds[0], 0, "new_map"))
+		goto cleanup;
+	prog_fd = __load_test_prog(extra_fds[0], extra_fds, 1);
+	if (!ASSERT_GE(prog_fd, 0, "BPF_PROG_LOAD"))
+		goto cleanup;
+	nr_map_ids = ARRAY_SIZE(map_ids);
+	if (!check_expected_map_ids(prog_fd, 1, map_ids, &nr_map_ids))
+		goto cleanup;
+
+	/* map should still exist when original file descriptor is closed */
+	Close(extra_fds[0]);
+	if (!ASSERT_EQ(map_exists(map_ids[0]), true, "map should exist"))
+		goto cleanup;
+
+	/* some fds might be invalid, so ignore return codes */
+cleanup:
+	Close(extra_fds[0]);
+	Close(prog_fd);
+}
+
+static int get_btf_id_by_fd(int btf_fd, __u32 *id)
+{
+	struct bpf_btf_info info;
+	__u32 info_len = sizeof(info);
+	int err;
+
+	memset(&info, 0, info_len);
+	err = bpf_btf_get_info_by_fd(btf_fd, &info, &info_len);
+	if (err)
+		return err;
+	if (id)
+		*id = info.id;
+	return 0;
+}
+
+/*
+ * Check that fd_array operates properly for btfs. Namely, to check that
+ * passing a btf fd in fd_array increases its reference count, do the
+ * following:
+ *  1) Create a new btf, it's referenced only by a file descriptor, so refcnt=1
+ *  2) Load a BPF prog with fd_array[0] = btf_fd; now btf's refcnt=2
+ *  3) Close the btf_fd, now refcnt=1
+ * Wait and check that BTF stil exists.
+ */
+static void check_fd_array_cnt__referenced_btfs(void)
+{
+	int extra_fds[1] = { -1 };
+	int prog_fd = -1;
+	__u32 btf_id;
+	int tries;
+	int err;
+
+	extra_fds[0] = new_btf();
+	if (!ASSERT_GE(extra_fds[0], 0, "new_btf"))
+		goto cleanup;
+	prog_fd = load_test_prog(extra_fds, 1);
+	if (!ASSERT_GE(prog_fd, 0, "BPF_PROG_LOAD"))
+		goto cleanup;
+
+	/* btf should still exist when original file descriptor is closed */
+	err = get_btf_id_by_fd(extra_fds[0], &btf_id);
+	if (!ASSERT_GE(err, 0, "get_btf_id_by_fd"))
+		goto cleanup;
+
+	Close(extra_fds[0]);
+
+	if (!ASSERT_GE(kern_sync_rcu(), 0, "kern_sync_rcu 1"))
+		goto cleanup;
+
+	if (!ASSERT_EQ(btf_exists(btf_id), true, "btf should exist"))
+		goto cleanup;
+
+	Close(prog_fd);
+
+	/* The program is freed by a workqueue, so no reliable
+	 * way to sync, so just wait a bit (max ~1 second). */
+	for (tries = 100; tries >= 0; tries--) {
+		usleep(1000);
+
+		if (!btf_exists(btf_id))
+			break;
+
+		if (tries)
+			continue;
+
+		PRINT_FAIL("btf should have been freed");
+	}
+
+	/* some fds might be invalid, so ignore return codes */
+cleanup:
+	Close(extra_fds[0]);
+	Close(prog_fd);
+}
+
+/*
+ * Test that a program with trash in fd_array can't be loaded:
+ * only map and BTF file descriptors should be accepted.
+ */
+static void check_fd_array_cnt__fd_array_with_trash(void)
+{
+	int extra_fds[3] = { -1, -1, -1 };
+	int prog_fd = -1;
+
+	extra_fds[0] = new_map();
+	if (!ASSERT_GE(extra_fds[0], 0, "new_map"))
+		goto cleanup;
+	extra_fds[1] = new_btf();
+	if (!ASSERT_GE(extra_fds[1], 0, "new_btf"))
+		goto cleanup;
+
+	/* trash 1: not a file descriptor */
+	extra_fds[2] = 0xbeef;
+	prog_fd = load_test_prog(extra_fds, 3);
+	if (!ASSERT_EQ(prog_fd, -EBADF, "prog should have been rejected with -EBADF"))
+		goto cleanup;
+
+	/* trash 2: not a map or btf */
+	extra_fds[2] = socket(AF_INET, SOCK_STREAM, 0);
+	if (!ASSERT_GE(extra_fds[2], 0, "socket"))
+		goto cleanup;
+
+	prog_fd = load_test_prog(extra_fds, 3);
+	if (!ASSERT_EQ(prog_fd, -EINVAL, "prog should have been rejected with -EINVAL"))
+		goto cleanup;
+
+	/* Validate that the prog is ok if trash is removed */
+	Close(extra_fds[2]);
+	extra_fds[2] = new_btf();
+	if (!ASSERT_GE(extra_fds[2], 0, "new_btf"))
+		goto cleanup;
+
+	prog_fd = load_test_prog(extra_fds, 3);
+	if (!ASSERT_GE(prog_fd, 0, "prog should have been loaded"))
+		goto cleanup;
+
+	/* some fds might be invalid, so ignore return codes */
+cleanup:
+	Close(extra_fds[2]);
+	Close(extra_fds[1]);
+	Close(extra_fds[0]);
+}
+
+/*
+ * Test that a program with too big fd_array can't be loaded.
+ */
+static void check_fd_array_cnt__fd_array_too_big(void)
+{
+	int extra_fds[65];
+	int prog_fd = -1;
+	int i;
+
+	for (i = 0; i < 65; i++) {
+		extra_fds[i] = new_map();
+		if (!ASSERT_GE(extra_fds[i], 0, "new_map"))
+			goto cleanup_fds;
+	}
+
+	prog_fd = load_test_prog(extra_fds, 65);
+	ASSERT_EQ(prog_fd, -E2BIG, "prog should have been rejected with -E2BIG");
+
+cleanup_fds:
+	while (i > 0)
+		Close(extra_fds[--i]);
+}
+
+void test_fd_array_cnt(void)
+{
+	if (test__start_subtest("no-fd-array"))
+		check_fd_array_cnt__no_fd_array();
+
+	if (test__start_subtest("fd-array-ok"))
+		check_fd_array_cnt__fd_array_ok();
+
+	if (test__start_subtest("fd-array-dup-input"))
+		check_fd_array_cnt__duplicated_maps();
+
+	if (test__start_subtest("fd-array-ref-maps-in-array"))
+		check_fd_array_cnt__referenced_maps_in_fd_array();
+
+	if (test__start_subtest("fd-array-ref-btfs"))
+		check_fd_array_cnt__referenced_btfs();
+
+	if (test__start_subtest("fd-array-trash-input"))
+		check_fd_array_cnt__fd_array_with_trash();
+
+	if (test__start_subtest("fd-array-2big"))
+		check_fd_array_cnt__fd_array_too_big();
+}