linux-kernel - Re: [PATCH bpf-next] bpf: btf: restore resolve

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Message-ID: <CAN+4W8jXG2dNTtksYtQPYQgpfGMKgMqLhW_jHJSY=HhZ6G9PeA@mail.gmail.com>
Date:   Tue, 16 May 2023 11:32:54 +0100
From:   Lorenz Bauer <lmb@...valent.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Martin KaFai Lau <martin.lau@...ux.dev>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next] bpf: btf: restore resolve_mode when popping the
 resolve stack

On Mon, May 15, 2023 at 8:26 PM Daniel Borkmann <daniel@...earbox.net> wrote:
>
> On 5/15/23 2:15 PM, Lorenz Bauer wrote:
> > In commit 9b459804ff99 ("btf: fix resolving BTF_KIND_VAR after ARRAY, STRUCT, UNION, PTR")
> > I fixed a bug that occurred during resolving of a DATASEC by strategically resetting
> > resolve_mode. This fixes the immediate bug but leaves us open to future bugs where
> > nested types have to be resolved.
>
> Lgtm, is there a way we could also craft a test case for this corner case?

There is a test for the datasec bug already, it went in with the
original patch. See commit dfdd608c3b36 ("selftests/bpf: check that
modifier resolves after pointer").

Not sure how to test this beyond that specific case.