selftests/bpf: Add tests for dynptr convenience helpers

Add various tests for the added dynptr convenience helpers.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230420071414.570108-6-joannelkoong@gmail.com

tools/testing/selftests/bpf/bpf_kfuncs.h

@@ -35,4 +35,10 @@ extern void *bpf_dynptr_slice(const struct bpf_dynptr *ptr, __u32 offset,
 extern void *bpf_dynptr_slice_rdwr(const struct bpf_dynptr *ptr, __u32 offset,
 			      void *buffer, __u32 buffer__szk) __ksym;
 
+extern int bpf_dynptr_adjust(const struct bpf_dynptr *ptr, __u32 start, __u32 end) __ksym;
+extern int bpf_dynptr_is_null(const struct bpf_dynptr *ptr) __ksym;
+extern int bpf_dynptr_is_rdonly(const struct bpf_dynptr *ptr) __ksym;
+extern __u32 bpf_dynptr_size(const struct bpf_dynptr *ptr) __ksym;
+extern int bpf_dynptr_clone(const struct bpf_dynptr *ptr, struct bpf_dynptr *clone__init) __ksym;
+
 #endif

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

@@ -20,6 +20,12 @@ static struct {
 	{"test_ringbuf", SETUP_SYSCALL_SLEEP},
 	{"test_skb_readonly", SETUP_SKB_PROG},
 	{"test_dynptr_skb_data", SETUP_SKB_PROG},
+	{"test_adjust", SETUP_SYSCALL_SLEEP},
+	{"test_adjust_err", SETUP_SYSCALL_SLEEP},
+	{"test_zero_size_dynptr", SETUP_SYSCALL_SLEEP},
+	{"test_dynptr_is_null", SETUP_SYSCALL_SLEEP},
+	{"test_dynptr_is_rdonly", SETUP_SKB_PROG},
+	{"test_dynptr_clone", SETUP_SKB_PROG},
 };
 
 static void verify_success(const char *prog_name, enum test_setup_type setup_type)

tools/testing/selftests/bpf/progs/dynptr_fail.c

@@ -1378,3 +1378,290 @@ int invalid_slice_rdwr_rdonly(struct __sk_buff *skb)
 
 	return 0;
 }
+
+/* bpf_dynptr_adjust can only be called on initialized dynptrs */
+SEC("?raw_tp")
+__failure __msg("Expected an initialized dynptr as arg #1")
+int dynptr_adjust_invalid(void *ctx)
+{
+	struct bpf_dynptr ptr;
+
+	/* this should fail */
+	bpf_dynptr_adjust(&ptr, 1, 2);
+
+	return 0;
+}
+
+/* bpf_dynptr_is_null can only be called on initialized dynptrs */
+SEC("?raw_tp")
+__failure __msg("Expected an initialized dynptr as arg #1")
+int dynptr_is_null_invalid(void *ctx)
+{
+	struct bpf_dynptr ptr;
+
+	/* this should fail */
+	bpf_dynptr_is_null(&ptr);
+
+	return 0;
+}
+
+/* bpf_dynptr_is_rdonly can only be called on initialized dynptrs */
+SEC("?raw_tp")
+__failure __msg("Expected an initialized dynptr as arg #1")
+int dynptr_is_rdonly_invalid(void *ctx)
+{
+	struct bpf_dynptr ptr;
+
+	/* this should fail */
+	bpf_dynptr_is_rdonly(&ptr);
+
+	return 0;
+}
+
+/* bpf_dynptr_size can only be called on initialized dynptrs */
+SEC("?raw_tp")
+__failure __msg("Expected an initialized dynptr as arg #1")
+int dynptr_size_invalid(void *ctx)
+{
+	struct bpf_dynptr ptr;
+
+	/* this should fail */
+	bpf_dynptr_size(&ptr);
+
+	return 0;
+}
+
+/* Only initialized dynptrs can be cloned */
+SEC("?raw_tp")
+__failure __msg("Expected an initialized dynptr as arg #1")
+int clone_invalid1(void *ctx)
+{
+	struct bpf_dynptr ptr1;
+	struct bpf_dynptr ptr2;
+
+	/* this should fail */
+	bpf_dynptr_clone(&ptr1, &ptr2);
+
+	return 0;
+}
+
+/* Can't overwrite an existing dynptr when cloning */
+SEC("?xdp")
+__failure __msg("cannot overwrite referenced dynptr")
+int clone_invalid2(struct xdp_md *xdp)
+{
+	struct bpf_dynptr ptr1;
+	struct bpf_dynptr clone;
+
+	bpf_dynptr_from_xdp(xdp, 0, &ptr1);
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, 64, 0, &clone);
+
+	/* this should fail */
+	bpf_dynptr_clone(&ptr1, &clone);
+
+	bpf_ringbuf_submit_dynptr(&clone, 0);
+
+	return 0;
+}
+
+/* Invalidating a dynptr should invalidate its clones */
+SEC("?raw_tp")
+__failure __msg("Expected an initialized dynptr as arg #3")
+int clone_invalidate1(void *ctx)
+{
+	struct bpf_dynptr clone;
+	struct bpf_dynptr ptr;
+	char read_data[64];
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr);
+
+	bpf_dynptr_clone(&ptr, &clone);
+
+	bpf_ringbuf_submit_dynptr(&ptr, 0);
+
+	/* this should fail */
+	bpf_dynptr_read(read_data, sizeof(read_data), &clone, 0, 0);
+
+	return 0;
+}
+
+/* Invalidating a dynptr should invalidate its parent */
+SEC("?raw_tp")
+__failure __msg("Expected an initialized dynptr as arg #3")
+int clone_invalidate2(void *ctx)
+{
+	struct bpf_dynptr ptr;
+	struct bpf_dynptr clone;
+	char read_data[64];
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr);
+
+	bpf_dynptr_clone(&ptr, &clone);
+
+	bpf_ringbuf_submit_dynptr(&clone, 0);
+
+	/* this should fail */
+	bpf_dynptr_read(read_data, sizeof(read_data), &ptr, 0, 0);
+
+	return 0;
+}
+
+/* Invalidating a dynptr should invalidate its siblings */
+SEC("?raw_tp")
+__failure __msg("Expected an initialized dynptr as arg #3")
+int clone_invalidate3(void *ctx)
+{
+	struct bpf_dynptr ptr;
+	struct bpf_dynptr clone1;
+	struct bpf_dynptr clone2;
+	char read_data[64];
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr);
+
+	bpf_dynptr_clone(&ptr, &clone1);
+
+	bpf_dynptr_clone(&ptr, &clone2);
+
+	bpf_ringbuf_submit_dynptr(&clone2, 0);
+
+	/* this should fail */
+	bpf_dynptr_read(read_data, sizeof(read_data), &clone1, 0, 0);
+
+	return 0;
+}
+
+/* Invalidating a dynptr should invalidate any data slices
+ * of its clones
+ */
+SEC("?raw_tp")
+__failure __msg("invalid mem access 'scalar'")
+int clone_invalidate4(void *ctx)
+{
+	struct bpf_dynptr ptr;
+	struct bpf_dynptr clone;
+	int *data;
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr);
+
+	bpf_dynptr_clone(&ptr, &clone);
+	data = bpf_dynptr_data(&clone, 0, sizeof(val));
+	if (!data)
+		return 0;
+
+	bpf_ringbuf_submit_dynptr(&ptr, 0);
+
+	/* this should fail */
+	*data = 123;
+
+	return 0;
+}
+
+/* Invalidating a dynptr should invalidate any data slices
+ * of its parent
+ */
+SEC("?raw_tp")
+__failure __msg("invalid mem access 'scalar'")
+int clone_invalidate5(void *ctx)
+{
+	struct bpf_dynptr ptr;
+	struct bpf_dynptr clone;
+	int *data;
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr);
+	data = bpf_dynptr_data(&ptr, 0, sizeof(val));
+	if (!data)
+		return 0;
+
+	bpf_dynptr_clone(&ptr, &clone);
+
+	bpf_ringbuf_submit_dynptr(&clone, 0);
+
+	/* this should fail */
+	*data = 123;
+
+	return 0;
+}
+
+/* Invalidating a dynptr should invalidate any data slices
+ * of its sibling
+ */
+SEC("?raw_tp")
+__failure __msg("invalid mem access 'scalar'")
+int clone_invalidate6(void *ctx)
+{
+	struct bpf_dynptr ptr;
+	struct bpf_dynptr clone1;
+	struct bpf_dynptr clone2;
+	int *data;
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr);
+
+	bpf_dynptr_clone(&ptr, &clone1);
+
+	bpf_dynptr_clone(&ptr, &clone2);
+
+	data = bpf_dynptr_data(&clone1, 0, sizeof(val));
+	if (!data)
+		return 0;
+
+	bpf_ringbuf_submit_dynptr(&clone2, 0);
+
+	/* this should fail */
+	*data = 123;
+
+	return 0;
+}
+
+/* A skb clone's data slices should be invalid anytime packet data changes */
+SEC("?tc")
+__failure __msg("invalid mem access 'scalar'")
+int clone_skb_packet_data(struct __sk_buff *skb)
+{
+	char buffer[sizeof(__u32)] = {};
+	struct bpf_dynptr clone;
+	struct bpf_dynptr ptr;
+	__u32 *data;
+
+	bpf_dynptr_from_skb(skb, 0, &ptr);
+
+	bpf_dynptr_clone(&ptr, &clone);
+	data = bpf_dynptr_slice_rdwr(&clone, 0, buffer, sizeof(buffer));
+	if (!data)
+		return XDP_DROP;
+
+	if (bpf_skb_pull_data(skb, skb->len))
+		return SK_DROP;
+
+	/* this should fail */
+	*data = 123;
+
+	return 0;
+}
+
+/* A xdp clone's data slices should be invalid anytime packet data changes */
+SEC("?xdp")
+__failure __msg("invalid mem access 'scalar'")
+int clone_xdp_packet_data(struct xdp_md *xdp)
+{
+	char buffer[sizeof(__u32)] = {};
+	struct bpf_dynptr clone;
+	struct bpf_dynptr ptr;
+	struct ethhdr *hdr;
+	__u32 *data;
+
+	bpf_dynptr_from_xdp(xdp, 0, &ptr);
+
+	bpf_dynptr_clone(&ptr, &clone);
+	data = bpf_dynptr_slice_rdwr(&clone, 0, buffer, sizeof(buffer));
+	if (!data)
+		return XDP_DROP;
+
+	if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(*hdr)))
+		return XDP_DROP;
+
+	/* this should fail */
+	*data = 123;
+
+	return 0;
+}

tools/testing/selftests/bpf/progs/dynptr_success.c

@@ -207,3 +207,301 @@ int test_dynptr_skb_data(struct __sk_buff *skb)
 
 	return 1;
 }
+
+SEC("tp/syscalls/sys_enter_nanosleep")
+int test_adjust(void *ctx)
+{
+	struct bpf_dynptr ptr;
+	__u32 bytes = 64;
+	__u32 off = 10;
+	__u32 trim = 15;
+
+	if (bpf_get_current_pid_tgid() >> 32 != pid)
+		return 0;
+
+	err = bpf_ringbuf_reserve_dynptr(&ringbuf, bytes, 0, &ptr);
+	if (err) {
+		err = 1;
+		goto done;
+	}
+
+	if (bpf_dynptr_size(&ptr) != bytes) {
+		err = 2;
+		goto done;
+	}
+
+	/* Advance the dynptr by off */
+	err = bpf_dynptr_adjust(&ptr, off, bpf_dynptr_size(&ptr));
+	if (err) {
+		err = 3;
+		goto done;
+	}
+
+	if (bpf_dynptr_size(&ptr) != bytes - off) {
+		err = 4;
+		goto done;
+	}
+
+	/* Trim the dynptr */
+	err = bpf_dynptr_adjust(&ptr, off, 15);
+	if (err) {
+		err = 5;
+		goto done;
+	}
+
+	/* Check that the size was adjusted correctly */
+	if (bpf_dynptr_size(&ptr) != trim - off) {
+		err = 6;
+		goto done;
+	}
+
+done:
+	bpf_ringbuf_discard_dynptr(&ptr, 0);
+	return 0;
+}
+
+SEC("tp/syscalls/sys_enter_nanosleep")
+int test_adjust_err(void *ctx)
+{
+	char write_data[45] = "hello there, world!!";
+	struct bpf_dynptr ptr;
+	__u32 size = 64;
+	__u32 off = 20;
+
+	if (bpf_get_current_pid_tgid() >> 32 != pid)
+		return 0;
+
+	if (bpf_ringbuf_reserve_dynptr(&ringbuf, size, 0, &ptr)) {
+		err = 1;
+		goto done;
+	}
+
+	/* Check that start can't be greater than end */
+	if (bpf_dynptr_adjust(&ptr, 5, 1) != -EINVAL) {
+		err = 2;
+		goto done;
+	}
+
+	/* Check that start can't be greater than size */
+	if (bpf_dynptr_adjust(&ptr, size + 1, size + 1) != -ERANGE) {
+		err = 3;
+		goto done;
+	}
+
+	/* Check that end can't be greater than size */
+	if (bpf_dynptr_adjust(&ptr, 0, size + 1) != -ERANGE) {
+		err = 4;
+		goto done;
+	}
+
+	if (bpf_dynptr_adjust(&ptr, off, size)) {
+		err = 5;
+		goto done;
+	}
+
+	/* Check that you can't write more bytes than available into the dynptr
+	 * after you've adjusted it
+	 */
+	if (bpf_dynptr_write(&ptr, 0, &write_data, sizeof(write_data), 0) != -E2BIG) {
+		err = 6;
+		goto done;
+	}
+
+	/* Check that even after adjusting, submitting/discarding
+	 * a ringbuf dynptr works
+	 */
+	bpf_ringbuf_submit_dynptr(&ptr, 0);
+	return 0;
+
+done:
+	bpf_ringbuf_discard_dynptr(&ptr, 0);
+	return 0;
+}
+
+SEC("tp/syscalls/sys_enter_nanosleep")
+int test_zero_size_dynptr(void *ctx)
+{
+	char write_data = 'x', read_data;
+	struct bpf_dynptr ptr;
+	__u32 size = 64;
+
+	if (bpf_get_current_pid_tgid() >> 32 != pid)
+		return 0;
+
+	if (bpf_ringbuf_reserve_dynptr(&ringbuf, size, 0, &ptr)) {
+		err = 1;
+		goto done;
+	}
+
+	/* After this, the dynptr has a size of 0 */
+	if (bpf_dynptr_adjust(&ptr, size, size)) {
+		err = 2;
+		goto done;
+	}
+
+	/* Test that reading + writing non-zero bytes is not ok */
+	if (bpf_dynptr_read(&read_data, sizeof(read_data), &ptr, 0, 0) != -E2BIG) {
+		err = 3;
+		goto done;
+	}
+
+	if (bpf_dynptr_write(&ptr, 0, &write_data, sizeof(write_data), 0) != -E2BIG) {
+		err = 4;
+		goto done;
+	}
+
+	/* Test that reading + writing 0 bytes from a 0-size dynptr is ok */
+	if (bpf_dynptr_read(&read_data, 0, &ptr, 0, 0)) {
+		err = 5;
+		goto done;
+	}
+
+	if (bpf_dynptr_write(&ptr, 0, &write_data, 0, 0)) {
+		err = 6;
+		goto done;
+	}
+
+	err = 0;
+
+done:
+	bpf_ringbuf_discard_dynptr(&ptr, 0);
+	return 0;
+}
+
+SEC("tp/syscalls/sys_enter_nanosleep")
+int test_dynptr_is_null(void *ctx)
+{
+	struct bpf_dynptr ptr1;
+	struct bpf_dynptr ptr2;
+	__u64 size = 4;
+
+	if (bpf_get_current_pid_tgid() >> 32 != pid)
+		return 0;
+
+	/* Pass in invalid flags, get back an invalid dynptr */
+	if (bpf_ringbuf_reserve_dynptr(&ringbuf, size, 123, &ptr1) != -EINVAL) {
+		err = 1;
+		goto exit_early;
+	}
+
+	/* Test that the invalid dynptr is null */
+	if (!bpf_dynptr_is_null(&ptr1)) {
+		err = 2;
+		goto exit_early;
+	}
+
+	/* Get a valid dynptr */
+	if (bpf_ringbuf_reserve_dynptr(&ringbuf, size, 0, &ptr2)) {
+		err = 3;
+		goto exit;
+	}
+
+	/* Test that the valid dynptr is not null */
+	if (bpf_dynptr_is_null(&ptr2)) {
+		err = 4;
+		goto exit;
+	}
+
+exit:
+	bpf_ringbuf_discard_dynptr(&ptr2, 0);
+exit_early:
+	bpf_ringbuf_discard_dynptr(&ptr1, 0);
+	return 0;
+}
+
+SEC("cgroup_skb/egress")
+int test_dynptr_is_rdonly(struct __sk_buff *skb)
+{
+	struct bpf_dynptr ptr1;
+	struct bpf_dynptr ptr2;
+	struct bpf_dynptr ptr3;
+
+	/* Pass in invalid flags, get back an invalid dynptr */
+	if (bpf_dynptr_from_skb(skb, 123, &ptr1) != -EINVAL) {
+		err = 1;
+		return 0;
+	}
+
+	/* Test that an invalid dynptr is_rdonly returns false */
+	if (bpf_dynptr_is_rdonly(&ptr1)) {
+		err = 2;
+		return 0;
+	}
+
+	/* Get a read-only dynptr */
+	if (bpf_dynptr_from_skb(skb, 0, &ptr2)) {
+		err = 3;
+		return 0;
+	}
+
+	/* Test that the dynptr is read-only */
+	if (!bpf_dynptr_is_rdonly(&ptr2)) {
+		err = 4;
+		return 0;
+	}
+
+	/* Get a read-writeable dynptr */
+	if (bpf_ringbuf_reserve_dynptr(&ringbuf, 64, 0, &ptr3)) {
+		err = 5;
+		goto done;
+	}
+
+	/* Test that the dynptr is read-only */
+	if (bpf_dynptr_is_rdonly(&ptr3)) {
+		err = 6;
+		goto done;
+	}
+
+done:
+	bpf_ringbuf_discard_dynptr(&ptr3, 0);
+	return 0;
+}
+
+SEC("cgroup_skb/egress")
+int test_dynptr_clone(struct __sk_buff *skb)
+{
+	struct bpf_dynptr ptr1;
+	struct bpf_dynptr ptr2;
+	__u32 off = 2, size;
+
+	/* Get a dynptr */
+	if (bpf_dynptr_from_skb(skb, 0, &ptr1)) {
+		err = 1;
+		return 0;
+	}
+
+	if (bpf_dynptr_adjust(&ptr1, off, bpf_dynptr_size(&ptr1))) {
+		err = 2;
+		return 0;
+	}
+
+	/* Clone the dynptr */
+	if (bpf_dynptr_clone(&ptr1, &ptr2)) {
+		err = 3;
+		return 0;
+	}
+
+	size = bpf_dynptr_size(&ptr1);
+
+	/* Check that the clone has the same size and rd-only */
+	if (bpf_dynptr_size(&ptr2) != size) {
+		err = 4;
+		return 0;
+	}
+
+	if (bpf_dynptr_is_rdonly(&ptr2) != bpf_dynptr_is_rdonly(&ptr1)) {
+		err = 5;
+		return 0;
+	}
+
+	/* Advance and trim the original dynptr */
+	bpf_dynptr_adjust(&ptr1, 5, 5);
+
+	/* Check that only original dynptr was affected, and the clone wasn't */
+	if (bpf_dynptr_size(&ptr2) != size) {
+		err = 6;
+		return 0;
+	}
+
+	return 0;
+}