[RFC PATCH bpf-next v2 08/11] selftests/bpf: Test creating dynptr from dynptr data and slice
From: Amery Hung <hidden>
Date: 2026-03-07 06:44:50
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
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 <redacted> --- .../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 631e37500ec6..6b162512b0c9 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_fail.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c@@ -704,6 +704,48 @@ 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)
--
2.47.3