[bpf-next,v3,12/12] selftests/bpf: Add dynptr helper tests

Commit Message

Kumar Kartikeya Dwivedi Jan. 20, 2023, 3:43 a.m. UTC

First test that we allow overwriting dynptr slots and reinitializing
them in unreferenced case, and disallow overwriting for referenced case.
Include tests to ensure slices obtained from destroyed dynptrs are being
invalidated on their destruction. The destruction needs to be scoped, as
in slices of dynptr A should not be invalidated when dynptr B is
destroyed. Next, test that MEM_UNINIT doesn't allow writing dynptr stack
slots.

Signed-off-by: Kumar Kartikeya Dwivedi <[e-mail]>
---
 .../testing/selftests/bpf/progs/dynptr_fail.c | 129 ++++++++++++++++++
 1 file changed, 129 insertions(+)

Patch

diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c
index cf2d12329a1e..928ba778179b 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_fail.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c
@@ -900,3 +900,132 @@  int dynptr_partial_slot_invalidate(struct __sk_buff *ctx)
 	);
 	return 0;
 }
+
+SEC("?raw_tp")
+__success
+int dynptr_overwrite_unref(void *ctx)
+{
+	struct bpf_dynptr ptr;
+
+	if (get_map_val_dynptr(&ptr))
+		return 0;
+	if (get_map_val_dynptr(&ptr))
+		return 0;
+	if (get_map_val_dynptr(&ptr))
+		return 0;
+
+	return 0;
+}
+
+SEC("?raw_tp")
+__failure __msg("R1 type=scalar expected=percpu_ptr_")
+int dynptr_invalidate_slice_or_null(void *ctx)
+{
+	struct bpf_dynptr ptr;
+	__u8 *p;
+
+	if (get_map_val_dynptr(&ptr))
+		return 0;
+
+	p = bpf_dynptr_data(&ptr, 0, 1);
+	*(__u8 *)&ptr = 0;
+	bpf_this_cpu_ptr(p);
+	return 0;
+}
+
+SEC("?raw_tp")
+__failure __msg("R7 invalid mem access 'scalar'")
+int dynptr_invalidate_slice_failure(void *ctx)
+{
+	struct bpf_dynptr ptr1;
+	struct bpf_dynptr ptr2;
+	__u8 *p1, *p2;
+
+	if (get_map_val_dynptr(&ptr1))
+		return 0;
+	if (get_map_val_dynptr(&ptr2))
+		return 0;
+
+	p1 = bpf_dynptr_data(&ptr1, 0, 1);
+	if (!p1)
+		return 0;
+	p2 = bpf_dynptr_data(&ptr2, 0, 1);
+	if (!p2)
+		return 0;
+
+	*(__u8 *)&ptr1 = 0;
+	return *p1;
+}
+
+SEC("?raw_tp")
+__success
+int dynptr_invalidate_slice_success(void *ctx)
+{
+	struct bpf_dynptr ptr1;
+	struct bpf_dynptr ptr2;
+	__u8 *p1, *p2;
+
+	if (get_map_val_dynptr(&ptr1))
+		return 1;
+	if (get_map_val_dynptr(&ptr2))
+		return 1;
+
+	p1 = bpf_dynptr_data(&ptr1, 0, 1);
+	if (!p1)
+		return 1;
+	p2 = bpf_dynptr_data(&ptr2, 0, 1);
+	if (!p2)
+		return 1;
+
+	*(__u8 *)&ptr1 = 0;
+	return *p2;
+}
+
+SEC("?raw_tp")
+__failure __msg("cannot overwrite referenced dynptr")
+int dynptr_overwrite_ref(void *ctx)
+{
+	struct bpf_dynptr ptr;
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, 64, 0, &ptr);
+	if (get_map_val_dynptr(&ptr))
+		bpf_ringbuf_discard_dynptr(&ptr, 0);
+	return 0;
+}
+
+/* Reject writes to dynptr slot from bpf_dynptr_read */
+SEC("?raw_tp")
+__failure __msg("potential write to dynptr at off=-16")
+int dynptr_read_into_slot(void *ctx)
+{
+	union {
+		struct {
+			char _pad[48];
+			struct bpf_dynptr ptr;
+		};
+		char buf[64];
+	} data;
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, 64, 0, &data.ptr);
+	/* this should fail */
+	bpf_dynptr_read(data.buf, sizeof(data.buf), &data.ptr, 0, 0);
+
+	return 0;
+}
+
+/* Reject writes to dynptr slot for uninit arg */
+SEC("?raw_tp")
+__failure __msg("potential write to dynptr at off=-16")
+int uninit_write_into_slot(void *ctx)
+{
+	struct {
+		char buf[64];
+		struct bpf_dynptr ptr;
+	} data;
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, 80, 0, &data.ptr);
+	/* this should fail */
+	bpf_get_current_comm(data.buf, 80);
+
+	return 0;
+}