[PATCH bpf-next v3 8/9] selftests/bpf: Test using slice after invalidating dynptr clone

Amery Hung
2026-04-21T22:10:27Z

The parent object of a cloned dynptr is skb not the original dynptr.
Invalidate the original dynptr should not prevent the program from
using the slice derived from the cloned dynptr.

Signed-off-by: Amery Hung <ameryhung@gmail.com>
---
.../selftests/bpf/prog_tests/bpf_qdisc.c | 2 +
..._qdisc_dynptr_use_after_invalidate_clone.c | 75 +++++++++++++++++++
2 files changed, 77 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/bpf_qdisc_dynptr_use_after_invalidate_clone.c

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
index 65277c8fc887..77f1c0550c9b 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
@@ -11,6 +11,7 @@
#include "bpf_qdisc_fail__invalid_dynptr.skel.h"
#include "bpf_qdisc_fail__invalid_dynptr_slice.skel.h"
#include "bpf_qdisc_fail__invalid_dynptr_cross_frame.skel.h"
+#include "bpf_qdisc_dynptr_use_after_invalidate_clone.skel.h"

#define LO_IFINDEX 1

@@ -229,6 +230,7 @@ void test_ns_bpf_qdisc(void)
RUN_TESTS(bpf_qdisc_fail__invalid_dynptr);
RUN_TESTS(bpf_qdisc_fail__invalid_dynptr_cross_frame);
RUN_TESTS(bpf_qdisc_fail__invalid_dynptr_slice);
+ RUN_TESTS(bpf_qdisc_dynptr_use_after_invalidate_clone);
}

void serial_test_bpf_qdisc_default(void)
diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_dynptr_use_after_invalidate_clone.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_dynptr_use_after_invalidate_clone.c
new file mode 100644
index 000000000000..cca2accf081d
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_dynptr_use_after_invalidate_clone.c
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <vmlinux.h>
+#include "bpf_experimental.h"
+#include "bpf_qdisc_common.h"
+#include "bpf_misc.h"
+
+char _license[] SEC("license") = "GPL";
+
+int proto;
+
+SEC("struct_ops")
+__success
+int BPF_PROG(dynptr_use_after_invalidate_clone, struct sk_buff *skb, struct Qdisc *sch,
+ struct bpf_sk_buff_ptr *to_free)
+{
+ struct bpf_dynptr ptr, ptr_clone;
+ struct ethhdr *hdr;
+
+ bpf_dynptr_from_skb((struct __sk_buff *)skb, 0, &ptr);
+
+ bpf_dynptr_clone(&ptr, &ptr_clone);
+
+ hdr = bpf_dynptr_slice(&ptr_clone, 0, NULL, sizeof(*hdr));
+ if (!hdr) {
+ bpf_qdisc_skb_drop(skb, to_free);
+ return NET_XMIT_DROP;
+ }
+
+ *(int *)&ptr = 0;
+
+ proto = hdr->h_proto;
+
+ bpf_qdisc_skb_drop(skb, to_free);
+
+ return NET_XMIT_DROP;
+}
+
+SEC("struct_ops")
+__auxiliary
+struct sk_buff *BPF_PROG(bpf_qdisc_test_dequeue, struct Qdisc *sch)
+{
+ return NULL;
+}
+
+SEC("struct_ops")
+__auxiliary
+int BPF_PROG(bpf_qdisc_test_init, struct Qdisc *sch, struct nlattr *opt,
+ struct netlink_ext_ack *extack)
+{
+ return 0;
+}
+
+SEC("struct_ops")
+__auxiliary
+void BPF_PROG(bpf_qdisc_test_reset, struct Qdisc *sch)
+{
+}
+
+SEC("struct_ops")
+__auxiliary
+void BPF_PROG(bpf_qdisc_test_destroy, struct Qdisc *sch)
+{
+}
+
+SEC(".struct_ops")
+struct Qdisc_ops test = {
+ .enqueue = (void *)dynptr_use_after_invalidate_clone,
+ .dequeue = (void *)bpf_qdisc_test_dequeue,
+ .init = (void *)bpf_qdisc_test_init,
+ .reset = (void *)bpf_qdisc_test_reset,
+ .destroy = (void *)bpf_qdisc_test_destroy,
+ .id = "bpf_qdisc_test",
+};
+
--
2.52.0