netdev - Re: [PATCH v2 bpf 0/2] Fix BTF verification of enum members with a selftest

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Date:   Tue, 10 Mar 2020 08:39:58 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Yoshiki Komachi <komachi.yoshiki@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH v2 bpf 0/2] Fix BTF verification of enum members with a selftest

On Tue, Mar 10, 2020 at 12:32 AM Yoshiki Komachi
<komachi.yoshiki@...il.com> wrote:
>
> btf_enum_check_member() checked if the size of "enum" as a struct
> member exceeded struct_size or not. Then, the function compared it
> with the size of "int". Although the size of "enum" is 4-byte by
> default (i.e., equivalent to "int"), the packing feature enables
> us to reduce it, as illustrated by the following example:
>
> struct A {
>         char m;
>         enum { E0, E1 } __attribute__((packed)) n;
> };
>
> With such a setup above, the bpf loader gave an error attempting
> to load it:
>
> ------------------------------------------------------------------
> ...
>
> [3] ENUM (anon) size=1 vlen=2
>         E0 val=0
>         E1 val=1
> [4] STRUCT A size=2 vlen=2
>         m type_id=2 bits_offset=0
>         n type_id=3 bits_offset=8
>
> [4] STRUCT A size=2 vlen=2
>         n type_id=3 bits_offset=8 Member exceeds struct_size
>
> libbpf: Error loading .BTF into kernel: -22.
>
> ------------------------------------------------------------------
>
> The related issue was previously fixed by the commit 9eea98497951 ("bpf:
> fix BTF verification of enums"). On the other hand, this series fixes
> this issue as well, and adds a selftest program for it.
>
> Changes in v2:
> - change an example in commit message based on Andrii's review
> - add a selftest program for packed "enum" type members in struct/union
>
> Yoshiki Komachi (2):
>   bpf/btf: Fix BTF verification of enum members in struct/union
>   selftests/bpf: Add test for the packed enum member in struct/union
>
>  kernel/bpf/btf.c                       |  2 +-
>  tools/testing/selftests/bpf/test_btf.c | 42 ++++++++++++++++++++++++++++++++++
>  2 files changed, 43 insertions(+), 1 deletion(-)
>
> --
> 1.8.3.1
>

You should have updated patch prefix for patch #1 and #2 to [PATCH v2
bpf] as well, please do it next time,

For the series:

Acked-by: Andrii Nakryiko <andriin@...com>