linux-hardening - Re: [REGRESSION] bpf verifier slowdown due to vrealloc() change since 6.15-rc6

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Message-ID: <202505150911.1254C695D@keescook>
Date: Thu, 15 May 2025 09:51:15 -0700
From: Kees Cook <kees@...nel.org>
To: Shung-Hsi Yu <shung-hsi.yu@...e.com>, bpf@...r.kernel.org,
	linux-mm@...ck.org, Andrii Nakryiko <andrii@...nel.org>,
	Ihor Solodrai <ihor.solodrai@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.com>, Vlastimil Babka <vbabka@...e.cz>,
	Uladzislau Rezki <urezki@...il.com>, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org, regressions@...ts.linux.dev,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
	Eduard Zingerman <eddyz87@...il.com>
Subject: Re: [REGRESSION] bpf verifier slowdown due to vrealloc() change
 since 6.15-rc6

On Thu, May 15, 2025 at 07:51:26AM -0700, Kees Cook wrote:
> On May 15, 2025 6:12:25 AM PDT, Shung-Hsi Yu <shung-hsi.yu@...e.com> wrote:
> >There is an observable slowdown when running BPF selftests on 6.15-rc6
> >kernel[1] built with tools/testing/selftests/bpf/{config,config.x86_64}.
> [...]
> Where can I find the .config for the slow runs?

Oops, I can read. :) Doing a build now...

> And how do I run the test myself directly?

I found:
https://docs.kernel.org/bpf/bpf_devel_QA.html

But it doesn't seem to cover a bunch of stuff (no way to prebuild the
tests, no info on building the test modules).

This seems to be needed:

make O=regression-bug -C tools/testing/selftests/bpf/test_kmods

But then the booted kernel doesn't load it (missing signatures?)

Anyway, I'll keep digging...

-- 
Kees Cook