[PATCH bpf-next v1 13/13] selftests/bpf: Add dynptr helper tests

[Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>]

Test that MEM_UNINIT doesn't allow writing dynptr stack slots. Next,
also add a test triggering the memmove case for dynptr_read and
dynptr_write.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
---
 .../testing/selftests/bpf/prog_tests/dynptr.c |  3 ++
 .../testing/selftests/bpf/progs/dynptr_fail.c | 35 +++++++++++++++++++
 .../selftests/bpf/progs/dynptr_success.c      | 20 +++++++++++
 3 files changed, 58 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/dynptr.c b/tools/testing/selftests/bpf/prog_tests/dynptr.c
index 947126d217bd..20910598a0a6 100644
--- a/tools/testing/selftests/bpf/prog_tests/dynptr.c
+++ b/tools/testing/selftests/bpf/prog_tests/dynptr.c
@@ -42,11 +42,14 @@ static struct {
 	{"release_twice_callback", "arg 1 is an unacquired reference"},
 	{"dynptr_from_mem_invalid_api",
 		"Unsupported reg type fp for bpf_dynptr_from_mem data"},
+	{"dynptr_read_into_slot", "potential write to dynptr at off=-16"},
+	{"uninit_write_into_slot", "potential write to dynptr at off=-16"},
 
 	/* success cases */
 	{"test_read_write", NULL},
 	{"test_data_slice", NULL},
 	{"test_ringbuf", NULL},
+	{"test_overlap", NULL},
 };
 
 static void verify_fail(const char *prog_name, const char *expected_err_msg)
diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c
index b0f08ff024fb..43a0ed3736a9 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_fail.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c
@@ -622,3 +622,38 @@ int dynptr_from_mem_invalid_api(void *ctx)
 
 	return 0;
 }
+
+/* Reject writes to dynptr slot from bpf_dynptr_read */
+SEC("?raw_tp")
+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")
+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;
+}
diff --git a/tools/testing/selftests/bpf/progs/dynptr_success.c b/tools/testing/selftests/bpf/progs/dynptr_success.c
index a3a6103c8569..401e924b15a0 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_success.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_success.c
@@ -162,3 +162,23 @@ int test_ringbuf(void *ctx)
 	bpf_ringbuf_discard_dynptr(&ptr, 0);
 	return 0;
 }
+
+SEC("tp/syscalls/sys_enter_nanosleep")
+int test_overlap(void *ctx)
+{
+	struct bpf_dynptr ptr;
+	void *p;
+
+	if (bpf_get_current_pid_tgid() >> 32 != pid)
+		return 0;
+	bpf_ringbuf_reserve_dynptr(&ringbuf, 16, 0, &ptr);
+	p = bpf_dynptr_data(&ptr, 0, 16);
+	if (!p) {
+		err = 1;
+		goto done;
+	}
+	bpf_dynptr_read(p + 1, 8, &ptr, 0, 0);
+done:
+	bpf_ringbuf_discard_dynptr(&ptr, 0);
+	return 0;
+}
-- 
2.38.0