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Tue, 21 Apr 2026 15:10:24 -0700 (PDT) Received: from localhost ([2a03:2880:ff:1::]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82f8e981d00sm14541222b3a.5.2026.04.21.15.10.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Apr 2026 15:10:24 -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 v3 6/9] selftests/bpf: Test creating dynptr from dynptr data and slice Date: Tue, 21 Apr 2026 15:10:13 -0700 Message-ID: <20260421221016.2967924-7-ameryhung@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260421221016.2967924-1-ameryhung@gmail.com> References: <20260421221016.2967924-1-ameryhung@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The verifier currently does not allow creating dynptr from dynptr data or slice. Add a selftest to test this explicitly. Signed-off-by: Amery Hung --- .../testing/selftests/bpf/progs/dynptr_fail.c | 42 +++++++++++++++++++ 1 file changed, 42 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c index b5fbc9b5c484..43beb70f50ee 100644 --- a/tools/testing/selftests/bpf/progs/dynptr_fail.c +++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c @@ -705,6 +705,48 @@ int dynptr_from_mem_invalid_api(void *ctx) return 0; } +/* Cannot create dynptr from dynptr data */ +SEC("?raw_tp") +__failure __msg("Unsupported reg type mem for bpf_dynptr_from_mem data") +int dynptr_from_dynptr_data(void *ctx) +{ + struct bpf_dynptr ptr, ptr2; + __u8 *data; + + if (get_map_val_dynptr(&ptr)) + return 0; + + data = bpf_dynptr_data(&ptr, 0, sizeof(__u32)); + if (!data) + return 0; + + /* this should fail */ + bpf_dynptr_from_mem(data, sizeof(__u32), 0, &ptr2); + + return 0; +} + +/* Cannot create dynptr from dynptr slice */ +SEC("?tc") +__failure __msg("Unsupported reg type mem for bpf_dynptr_from_mem data") +int dynptr_from_dynptr_slice(struct __sk_buff *skb) +{ + struct bpf_dynptr ptr, ptr2; + struct ethhdr *hdr; + char buffer[sizeof(*hdr)] = {}; + + bpf_dynptr_from_skb(skb, 0, &ptr); + + hdr = bpf_dynptr_slice_rdwr(&ptr, 0, buffer, sizeof(buffer)); + if (!hdr) + return SK_DROP; + + /* this should fail */ + bpf_dynptr_from_mem(hdr, sizeof(*hdr), 0, &ptr2); + + return SK_PASS; +} + SEC("?tc") __failure __msg("cannot overwrite referenced dynptr") __log_level(2) int dynptr_pruning_overwrite(struct __sk_buff *ctx) -- 2.52.0