[RFC PATCH bpf-next v2 09/11] selftests/bpf: Test using dynptr after freeing the underlying object
From: Amery Hung <hidden>
Date: 2026-03-07 06:44:51
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Linus Torvalds
Make sure the verifier invalidates the dynptr and dynptr slice derived from an skb after the skb is freed. Signed-off-by: Amery Hung <redacted> --- .../selftests/bpf/prog_tests/bpf_qdisc.c | 36 ++++++++++ .../progs/bpf_qdisc_fail__invalid_dynptr.c | 62 +++++++++++++++++ ...f_qdisc_fail__invalid_dynptr_cross_frame.c | 68 +++++++++++++++++++ .../bpf_qdisc_fail__invalid_dynptr_slice.c | 64 +++++++++++++++++ 4 files changed, 230 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr.c create mode 100644 tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_cross_frame.c create mode 100644 tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_slice.c
diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
index 730357cd0c9a..ec5b346138c5 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c@@ -8,6 +8,9 @@ #include "bpf_qdisc_fifo.skel.h" #include "bpf_qdisc_fq.skel.h" #include "bpf_qdisc_fail__incompl_ops.skel.h" +#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" #define LO_IFINDEX 1
@@ -156,6 +159,33 @@ static void test_incompl_ops(void) bpf_qdisc_fail__incompl_ops__destroy(skel); } +static void test_invalid_dynptr(void) +{ + struct bpf_qdisc_fail__invalid_dynptr *skel; + + skel = bpf_qdisc_fail__invalid_dynptr__open_and_load(); + if (!ASSERT_ERR_PTR(skel, "bpf_qdisc_fail__invalid_dynptr__open_and_load")) + bpf_qdisc_fail__invalid_dynptr__destroy(skel); +} + +static void test_invalid_dynptr_slice(void) +{ + struct bpf_qdisc_fail__invalid_dynptr_slice *skel; + + skel = bpf_qdisc_fail__invalid_dynptr_slice__open_and_load(); + if (!ASSERT_ERR_PTR(skel, "bpf_qdisc_fail__invalid_dynptr_slice__open_and_load")) + bpf_qdisc_fail__invalid_dynptr_slice__destroy(skel); +} + +static void test_invalid_dynptr_cross_frame(void) +{ + struct bpf_qdisc_fail__invalid_dynptr_cross_frame *skel; + + skel = bpf_qdisc_fail__invalid_dynptr_cross_frame__open_and_load(); + if (!ASSERT_ERR_PTR(skel, "bpf_qdisc_fail__invalid_dynptr_cross_frame__open_and_load")) + bpf_qdisc_fail__invalid_dynptr_cross_frame__destroy(skel); +} + static int get_default_qdisc(char *qdisc_name) { FILE *f;
@@ -223,6 +253,12 @@ void test_ns_bpf_qdisc(void) test_qdisc_attach_to_non_root(); if (test__start_subtest("incompl_ops")) test_incompl_ops(); + if (test__start_subtest("invalid_dynptr")) + test_invalid_dynptr(); + if (test__start_subtest("invalid_dynptr_slice")) + test_invalid_dynptr_slice(); + if (test__start_subtest("invalid_dynptr_cross_frame")) + test_invalid_dynptr_cross_frame(); } void serial_test_bpf_qdisc_default(void)
diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr.c
new file mode 100644
index 000000000000..2e76470bc261
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr.c@@ -0,0 +1,62 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <vmlinux.h> +#include "bpf_experimental.h" +#include "bpf_qdisc_common.h" + +char _license[] SEC("license") = "GPL"; + +int proto; + +SEC("struct_ops") +int BPF_PROG(bpf_qdisc_test_enqueue, struct sk_buff *skb, struct Qdisc *sch, + struct bpf_sk_buff_ptr *to_free) +{ + struct bpf_dynptr ptr; + struct ethhdr *hdr; + + bpf_dynptr_from_skb((struct __sk_buff *)skb, 0, &ptr); + + bpf_qdisc_skb_drop(skb, to_free); + + hdr = bpf_dynptr_slice(&ptr, 0, NULL, sizeof(*hdr)); + if (!hdr) + return NET_XMIT_DROP; + + proto = hdr->h_proto; + + return NET_XMIT_DROP; +} + +SEC("struct_ops") +struct sk_buff *BPF_PROG(bpf_qdisc_test_dequeue, struct Qdisc *sch) +{ + return NULL; +} + +SEC("struct_ops") +int BPF_PROG(bpf_qdisc_test_init, struct Qdisc *sch, struct nlattr *opt, + struct netlink_ext_ack *extack) +{ + return 0; +} + +SEC("struct_ops") +void BPF_PROG(bpf_qdisc_test_reset, struct Qdisc *sch) +{ +} + +SEC("struct_ops") +void BPF_PROG(bpf_qdisc_test_destroy, struct Qdisc *sch) +{ +} + +SEC(".struct_ops") +struct Qdisc_ops test = { + .enqueue = (void *)bpf_qdisc_test_enqueue, + .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", +};
diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_cross_frame.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_cross_frame.c
new file mode 100644
index 000000000000..565dea13bde8
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_cross_frame.c@@ -0,0 +1,68 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <vmlinux.h> +#include "bpf_experimental.h" +#include "bpf_qdisc_common.h" + +char _license[] SEC("license") = "GPL"; + +int proto; + +static __noinline int free_skb(struct sk_buff *skb) +{ + bpf_kfree_skb(skb); + return 0; +} + +SEC("struct_ops") +int BPF_PROG(bpf_qdisc_test_enqueue, struct sk_buff *skb, struct Qdisc *sch, + struct bpf_sk_buff_ptr *to_free) +{ + struct bpf_dynptr ptr; + struct ethhdr *hdr; + + bpf_dynptr_from_skb((struct __sk_buff *)skb, 0, &ptr); + + hdr = bpf_dynptr_slice(&ptr, 0, NULL, sizeof(*hdr)); + if (!hdr) + return NET_XMIT_DROP; + + free_skb(skb); + + proto = hdr->h_proto; + + return NET_XMIT_DROP; +} + +SEC("struct_ops") +struct sk_buff *BPF_PROG(bpf_qdisc_test_dequeue, struct Qdisc *sch) +{ + return NULL; +} + +SEC("struct_ops") +int BPF_PROG(bpf_qdisc_test_init, struct Qdisc *sch, struct nlattr *opt, + struct netlink_ext_ack *extack) +{ + return 0; +} + +SEC("struct_ops") +void BPF_PROG(bpf_qdisc_test_reset, struct Qdisc *sch) +{ +} + +SEC("struct_ops") +void BPF_PROG(bpf_qdisc_test_destroy, struct Qdisc *sch) +{ +} + +SEC(".struct_ops") +struct Qdisc_ops test = { + .enqueue = (void *)bpf_qdisc_test_enqueue, + .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", +};
diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_slice.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_slice.c
new file mode 100644
index 000000000000..95e8c070a37d
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_slice.c@@ -0,0 +1,64 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <vmlinux.h> +#include "bpf_experimental.h" +#include "bpf_qdisc_common.h" + +char _license[] SEC("license") = "GPL"; + +int proto; + +SEC("struct_ops") +int BPF_PROG(bpf_qdisc_test_enqueue, struct sk_buff *skb, struct Qdisc *sch, + struct bpf_sk_buff_ptr *to_free) +{ + struct bpf_dynptr ptr; + struct ethhdr *hdr; + + bpf_dynptr_from_skb((struct __sk_buff *)skb, 0, &ptr); + + hdr = bpf_dynptr_slice(&ptr, 0, NULL, sizeof(*hdr)); + if (!hdr) { + bpf_qdisc_skb_drop(skb, to_free); + return NET_XMIT_DROP; + } + + bpf_qdisc_skb_drop(skb, to_free); + + proto = hdr->h_proto; + + return NET_XMIT_DROP; +} + +SEC("struct_ops") +struct sk_buff *BPF_PROG(bpf_qdisc_test_dequeue, struct Qdisc *sch) +{ + return NULL; +} + +SEC("struct_ops") +int BPF_PROG(bpf_qdisc_test_init, struct Qdisc *sch, struct nlattr *opt, + struct netlink_ext_ack *extack) +{ + return 0; +} + +SEC("struct_ops") +void BPF_PROG(bpf_qdisc_test_reset, struct Qdisc *sch) +{ +} + +SEC("struct_ops") +void BPF_PROG(bpf_qdisc_test_destroy, struct Qdisc *sch) +{ +} + +SEC(".struct_ops") +struct Qdisc_ops test = { + .enqueue = (void *)bpf_qdisc_test_enqueue, + .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", +};
--
2.47.3