[RFC PATCH bpf-next/net v1 04/13] selftests/bpf: Add tests for dynptr source object interaction

[Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>]

Add a few tests to capture source object relationship with dynptr and
their slices and ensure invalidation of everything works correctly.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
---
 .../testing/selftests/bpf/prog_tests/dynptr.c |  2 +
 .../testing/selftests/bpf/progs/dynptr_fail.c |  1 +
 .../selftests/bpf/progs/dynptr_fail_qdisc.c   | 38 +++++++++++++++++++
 3 files changed, 41 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/dynptr_fail_qdisc.c

diff --git a/tools/testing/selftests/bpf/prog_tests/dynptr.c b/tools/testing/selftests/bpf/prog_tests/dynptr.c
index e29cc16124c2..929355de1002 100644
--- a/tools/testing/selftests/bpf/prog_tests/dynptr.c
+++ b/tools/testing/selftests/bpf/prog_tests/dynptr.c
@@ -4,6 +4,7 @@
 #include <test_progs.h>
 #include <network_helpers.h>
 #include "dynptr_fail.skel.h"
+#include "dynptr_fail_qdisc.skel.h"
 #include "dynptr_success.skel.h"
 
 enum test_setup_type {
@@ -161,4 +162,5 @@ void test_dynptr(void)
 	}
 
 	RUN_TESTS(dynptr_fail);
+	RUN_TESTS(dynptr_fail_qdisc);
 }
diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c
index 345e704e5346..7c67797a5aac 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_fail.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c
@@ -8,6 +8,7 @@
 #include <bpf/bpf_tracing.h>
 #include "bpf_misc.h"
 #include "bpf_kfuncs.h"
+#include "bpf_experimental.h"
 
 char _license[] SEC("license") = "GPL";
 
diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail_qdisc.c b/tools/testing/selftests/bpf/progs/dynptr_fail_qdisc.c
new file mode 100644
index 000000000000..fc222213f572
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/dynptr_fail_qdisc.c
@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "bpf_misc.h"
+#include "bpf_experimental.h"
+
+char _license[] SEC("license") = "GPL";
+
+/*
+ * Putting these tests in dynptr_fail.c causes other random tests to fail,
+ * keep them in their isolated CU.
+ */
+
+SEC("?struct_ops")
+__failure __msg("invalid mem access 'scalar'")
+int BPF_PROG(test_dynptr_source_release, struct sk_buff *skb,
+	     struct Qdisc *sch, struct bpf_sk_buff_ptr *to_free)
+{
+	struct bpf_dynptr dptr, dptr2;
+	char buf[8], *data;
+
+	bpf_dynptr_from_skb((struct __sk_buff *)skb, 0, &dptr);
+	bpf_dynptr_read(buf, sizeof(buf), &dptr, 0, 0);
+	bpf_dynptr_clone(&dptr, &dptr2);
+	data = bpf_dynptr_slice(&dptr2, 0, buf, sizeof(buf));
+	bpf_qdisc_skb_drop(skb, to_free);
+	/* These reads/writes now succeed since dynptr is destroyed. */
+	*(char *)&dptr = *(char *)&dptr2;
+	return *data;
+}
+
+SEC("?.struct_ops")
+struct Qdisc_ops test_dynptr_qdisc = {
+	.enqueue   = (void *)test_dynptr_source_release,
+	.id        = "bpf_fq",
+};
-- 
2.47.1