linux-kernel - Re: [PATCH 09/13] x86/kconfig/64: Enable popular MM options in the defconfig

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Message-ID: <CAG48ez1do372y_ow37tEdkyfUOHrwtLXBWH8PfnwwAN1ApT8Lg@mail.gmail.com>
Date: Mon, 16 Jun 2025 20:34:04 +0200
From: Jann Horn <jannh@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>, Kees Cook <keescook@...omium.org>, 
	linux-kernel@...r.kernel.org, "H . Peter Anvin" <hpa@...or.com>, 
	Linus Torvalds <torvalds@...ux-foundation.org>, Borislav Petkov <bp@...en8.de>, 
	Thomas Gleixner <tglx@...utronix.de>, Vitaly Kuznetsov <vkuznets@...hat.com>, 
	Jürgen Groß <jgross@...e.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Ard Biesheuvel <ardb@...nel.org>, 
	Arnd Bergmann <arnd@...db.de>, David Woodhouse <dwmw@...zon.co.uk>, 
	Masahiro Yamada <yamada.masahiro@...ionext.com>, Michal Marek <michal.lkml@...kovi.net>, 
	Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH 09/13] x86/kconfig/64: Enable popular MM options in the defconfig

On Sat, Jun 14, 2025 at 12:39 PM Peter Zijlstra <peterz@...radead.org> wrote:
> On Thu, May 15, 2025 at 03:27:15PM +0200, Ingo Molnar wrote:
> > Since the x86 defconfig aims to be a distro kernel work-alike with
> > fewer drivers and a shorter build time, enable the following
> > MM options that are typically enabled on major Linux distributions:
> >
> > - ACPI_HOTPLUG_MEMORY, ZSWAP, SLAB hardening, MEMORY_HOTPLUG,
> >   MEMORY_HOTREMOVE, PAGE_REPORTING, KSM, higher DEFAULT_MMAP_MIN_ADDR,
> >   MEMORY_FAILURE, HWPOISON_INJECT, TRANSPARENT_HUGEPAGE,
> >   TRANSPARENT_HUGEPAGE_MADVISE, IDLE_PAGE_TRACKING, ZONE_DEVICE
> >   DEVICE_PRIVATE, ANON_VMA_NAME, USERFAULTFD, multi-gen LRU.
> >
> > Signed-off-by: Ingo Molnar <mingo@...nel.org>
>
> > +CONFIG_KSM=y
>
> Isn't this thing like a giant security fail?

Yeah. (Though to actually do anything interesting, it requires root to
opt-in by enabling it through sysfs, and also requires the application
to opt in.)