Re: [PATCH net-next 05/15] selftests/bpf: Basic tests for metadata passing with gated skb tracepoints

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] bpf: ineffective map emptiness check in assert_meta_stash_empty()
--

commit 79ae30674787d12e96bd4c0fbc9d3bd7fe424d9c
Author: Jakub Sitnicki <jakub@cloudflare.com>

selftests/bpf: Basic tests for metadata passing with gated skb tracepoints

This commit adds tests for metadata passing where test programs stash
per-packet metadata in a hash map. It covers device round trips and clones
by propagating entries from the copy tracepoint and reclaiming them from
the free tracepoint.

> diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
> index 448807676176c..c9b115c14acb6 100644
> --- a/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
> +++ b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
[ ... ]
> @@ -693,3 +704,147 @@ void test_xdp_context_lwt_encap(void)
>  
>  	test_xdp_meta__destroy(skel);
>  }
> +
> +/* Assert that the free tracepoint prog drained the metadata stash */
> +static void assert_meta_stash_empty(struct bpf_map *meta_map)
> +{
> +	struct bpf_map_info info = {};
> +	__u32 info_len = sizeof(info);
> +
> +	if (!ASSERT_OK(bpf_map_get_info_by_fd(bpf_map__fd(meta_map), &info,
> +					      &info_len),
> +		       "get_info"))
> +		return;
> +
> +	ASSERT_EQ(info.map_extra, 0, "meta_map not empty");

[Severity: Medium]
Is this map emptiness check effectively a no-op?

For BPF_MAP_TYPE_RHASH maps, info.map_extra reflects the static nelem_hint
configuration parameter set during map creation, rather than the dynamic
number of elements currently residing in the map.

Since the meta_map is not configured with a map_extra attribute, won't it
default to 0 and remain 0 indefinitely, causing this assertion to always
pass even if map elements are actually leaked?

> +}
> +
> +static void test_skb_trace__tuntap(struct test_xdp_meta *skel)
[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260928-bpf-meta-gated-tracepoints-v1-0-844dbf3e1edf@cloudflare.com?part=5