linux-kernel - Re: [PATCH 1/1] uprobes: relax valid_vma check for VM

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Message-ID: <20250714083022.GJ905792@noisy.programming.kicks-ass.net>
Date: Mon, 14 Jul 2025 10:30:22 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Matt Gilbride <mattgilbride@...gle.com>
Cc: Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andrii Nakryiko <andrii@...nel.org>,
	David Hildenbrand <david@...hat.com>
Subject: Re: [PATCH 1/1] uprobes: relax valid_vma check for VM_MAYSHARE

On Fri, Jul 11, 2025 at 08:07:05PM +0000, Matt Gilbride wrote:
> ART maps a memfd twice, once as RW and once as RX, to uphold W^X for
> security (defense in depth),

I'll argue this is no defence at all. As long as there is a writable
mapping for an executable page, you've lost. You have effectively
violated W^X.