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selftests/bpf: Test creating dynptr from dynptr data and slice

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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 <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260529014936.2811085-11-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Amery Hung 2026-05-28 18:49:33 -07:00 committed by Alexei Starovoitov
parent 2eee6fe8ac
commit fbcc68af60
1 changed files with 42 additions and 0 deletions
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42
tools/testing/selftests/bpf/progs/dynptr_fail.c
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@ -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)