netdev - Re: [PATCH bpf v3 2/2] selftests/bpf: Add test cases to assert proper ID tracking on spill

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Date: Tue, 6 Jun 2023 18:43:51 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Maxim Mikityanskiy <maxtram95@...il.com>
Cc: bpf <bpf@...r.kernel.org>, Network Development <netdev@...r.kernel.org>, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	John Fastabend <john.fastabend@...il.com>, Alexei Starovoitov <ast@...nel.org>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Maxim Mikityanskiy <maxim@...valent.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yhs@...com>, KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, 
	Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, Mykola Lysenko <mykolal@...com>, 
	Shuah Khan <shuah@...nel.org>, "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Jesper Dangaard Brouer <hawk@...nel.org>
Subject: Re: [PATCH bpf v3 2/2] selftests/bpf: Add test cases to assert proper
 ID tracking on spill

On Tue, Jun 6, 2023 at 2:43 PM Maxim Mikityanskiy <maxtram95@...il.com> wrote:
>
> From: Maxim Mikityanskiy <maxim@...valent.com>
>
> The previous commit fixed a verifier bypass by ensuring that ID is not
> preserved on narrowing spills. Add the test cases to check the
> problematic patterns.
>
> Signed-off-by: Maxim Mikityanskiy <maxim@...valent.com>
> ---
>  .../selftests/bpf/progs/verifier_spill_fill.c | 198 ++++++++++++++++++
>  1 file changed, 198 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
> index 136e5530b72c..999677acc8ae 100644
> --- a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
> +++ b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
> @@ -371,4 +371,202 @@ __naked void and_then_at_fp_8(void)
>  "      ::: __clobber_all);
>  }
>
> +SEC("xdp")
> +__description("32-bit spill of 64-bit reg should clear ID")
> +__failure __msg("math between ctx pointer and 4294967295 is not allowed")
> +__naked void spill_32bit_of_64bit_fail(void)

It's an overkill to test all possible combinations.
32_of_64 and 16_of_32 would be enough.