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

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Message-ID: <202505151435.ECC98E09@keescook>
Date: Thu, 15 May 2025 14:36:19 -0700
From: Kees Cook <kees@...nel.org>
To: Eduard Zingerman <eddyz87@...il.com>
Cc: 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>,
	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>
Subject: Re: [REGRESSION] bpf verifier slowdown due to vrealloc() change
 since 6.15-rc6

On Thu, May 15, 2025 at 11:31:09AM -0700, Eduard Zingerman wrote:
> On Thu, 2025-05-15 at 08:47 -0700, Kees Cook wrote:
> > On Thu, May 15, 2025 at 09:12:25PM +0800, Shung-Hsi Yu wrote:
> > > Bisect was done by Pawan and got to commit a0309faf1cb0 "mm: vmalloc:
> > > support more granular vrealloc() sizing"[2]. To further zoom in the
> > 
> > Can you try this patch? It's a clear bug fix, but if it doesn't improve
> > things, I have another idea to rearrange the memset.
> 
> I tried this patch on top of the commit 82f2b0b97b36 ("Linux 6.15-rc6").
> W/o the patch I observe the slowdown, test times out after 120 seconds,
> with the patch test finishes in 3 seconds.

Well that's pretty definitive! Thank you! I'll send out a properly
formatted patch. May I add your Tested-by?

-- 
Kees Cook