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Thu, 28 May 2026 18:49:53 -0700 (PDT) Received: from localhost ([2a03:2880:ff:41::]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c85771a7af3sm119510a12.5.2026.05.28.18.49.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 May 2026 18:49:52 -0700 (PDT) From: Amery Hung To: bpf@vger.kernel.org Cc: netdev@vger.kernel.org, alexei.starovoitov@gmail.com, andrii@kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, memxor@gmail.com, martin.lau@kernel.org, mykyta.yatsenko5@gmail.com, ameryhung@gmail.com, kernel-team@meta.com Subject: [PATCH bpf-next v6 13/13] selftests/bpf: Test using dynptr after freeing the underlying object Date: Thu, 28 May 2026 18:49:36 -0700 Message-ID: <20260529014936.2811085-14-ameryhung@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260529014936.2811085-1-ameryhung@gmail.com> References: <20260529014936.2811085-1-ameryhung@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Make sure the verifier invalidates the dynptr and dynptr slice derived from an skb after the skb is freed. Signed-off-by: Amery Hung --- .../progs/bpf_qdisc_fail__invalid_dynptr.c | 68 +++++++++++++++++ ...f_qdisc_fail__invalid_dynptr_cross_frame.c | 74 +++++++++++++++++++ .../bpf_qdisc_fail__invalid_dynptr_slice.c | 70 ++++++++++++++++++ 3 files changed, 212 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/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..1d96f7987a3f --- /dev/null +++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr.c @@ -0,0 +1,68 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include "bpf_experimental.h" +#include "bpf_qdisc_common.h" +#include "bpf_misc.h" + +char _license[] SEC("license") = "GPL"; + +int proto; + +SEC("struct_ops") +__failure __msg("Expected an initialized dynptr as R1") +int BPF_PROG(invalid_dynptr, 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") +__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 *)invalid_dynptr, + .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..2e23b8593af9 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_cross_frame.c @@ -0,0 +1,74 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include "bpf_experimental.h" +#include "bpf_qdisc_common.h" +#include "bpf_misc.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") +__failure __msg("invalid mem access 'scalar'") +int BPF_PROG(invalid_dynptr_cross_frame, 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") +__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 *)invalid_dynptr_cross_frame, + .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..731216c4e45a --- /dev/null +++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_slice.c @@ -0,0 +1,70 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include "bpf_experimental.h" +#include "bpf_qdisc_common.h" +#include "bpf_misc.h" + +char _license[] SEC("license") = "GPL"; + +int proto; + +SEC("struct_ops") +__failure __msg("invalid mem access 'scalar'") +int BPF_PROG(invalid_dynptr_slice, 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") +__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 *)invalid_dynptr_slice, + .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", +}; -- 2.53.0-Meta