linux-kernel - Re: [PATCH bpf v3 2/2] selftests/bpf: fix and consolidate d

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Message-ID: <CAPhsuW75em0udAv2kuL04wPfDD2AKeSCkcsHjfPSh6nuTjNqtw@mail.gmail.com>
Date: Thu, 4 Dec 2025 13:41:39 -0800
From: Song Liu <song@...nel.org>
To: Shuran Liu <electronlsr@...il.com>
Cc: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org, 
	daniel@...earbox.net, dxu@...uu.xyz, eddyz87@...il.com, ftyg@...e.com, 
	gplhust955@...il.com, haoluo@...gle.com, haoran.ni.cs@...il.com, 
	john.fastabend@...il.com, jolsa@...nel.org, kpsingh@...nel.org, 
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org, martin.lau@...ux.dev, 
	mathieu.desnoyers@...icios.com, mattbobrowski@...gle.com, mhiramat@...nel.org, 
	rostedt@...dmis.org, sdf@...ichev.me, shuah@...nel.org, 
	yonghong.song@...ux.dev
Subject: Re: [PATCH bpf v3 2/2] selftests/bpf: fix and consolidate d_path LSM
 regression test

On Wed, Dec 3, 2025 at 8:34 PM Shuran Liu <electronlsr@...il.com> wrote:
>
> Hi Song,
>
> Thanks for the review.
>
> > I don't get why we add this selftest here. It doesn't appear to be related to
> > patch 1/2.
>
> The regression that patch 1/2 fixes was originally hit by an LSM program
> calling bpf_d_path() from the bprm_check_security hook. The new subtest is a
> minimal reproducer for that scenario: without patch 1/2 the string comparison
> never matches due to verifier's faulty optimization, and with patch 1/2 it
> behaves correctly.

I somehow didn't reproduce this in my local tests. Thanks for the explanation.

Song