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From: Chris Down <chris@chrisdown.name>
To: Kees Cook <kees@kernel.org>
Cc: Vlastimil Babka <vbabka@kernel.org>, Harry Yoo <harry@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Hao Li <hao.li@linux.dev>, Christoph Lameter <cl@gentwo.org>,
	David Rientjes <rientjes@google.com>,
	Roman Gushchin <roman.gushchin@linux.dev>,
	Marco Elver <elver@google.com>,
	GONG Ruiqi <gongruiqi@huaweicloud.com>,
	Jonathan Corbet <corbet@lwn.net>,
	linux-mm@kvack.org, linux-hardening@vger.kernel.org,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	kernel-team@meta.com
Subject: Re: [PATCH v2 2/6] mm/slab: Enable SLAB_FREELIST_RANDOM by default
Date: Fri, 13 Nov 2026 00:51:54 -0800	[thread overview]
Message-ID: <20261113005154.79ad6432034bf65c@chrisdown.name> (raw)
In-Reply-To: <202610302113.FB347BE5@keescook>

Hi Kees,

Kees Cook writes:
>Again, just like it should be. I wonder, though, don't these 2 changes
>undercut the goal of making these boot-time selectable?

I don't think so. The goal is to stop needing separate images for hosts
with different needs. It was never to make every option switchable for
its own sake. For these two, the only real argument for leaving them out
was CPU cost, and with sheaves that cost doesn't show up at the system
level [1]. So turning them on everywhere removes the reason to build
without them at all. Anyone who still wants them off can still say n at
build time.

SLAB_BUCKETS and KMALLOC_PARTITION_CACHES are different. Their cost is
memory, which is real and doesn't go away with sheaves, so those are the
ones where a boot time switch makes sense.

[1] https://lore.kernel.org/r/auITixAJMfLtfa7i@chrisdown.name

Thanks for the review!

Chris

  reply	other threads:[~2026-11-13  8:51 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-29  6:07 [PATCH v2 0/6] mm/slab: Support selecting slab hardening features at boot Chris Down
2026-10-29  6:07 ` [PATCH v2 1/6] mm/slab: Enable SLAB_FREELIST_HARDENED by default Chris Down
2026-10-31  4:13   ` Kees Cook
2026-10-29  6:07 ` [PATCH v2 2/6] mm/slab: Enable SLAB_FREELIST_RANDOM " Chris Down
2026-10-31  4:15   ` Kees Cook
2026-11-13  8:51     ` Chris Down [this message]
2026-10-29  6:08 ` [PATCH v2 3/6] mm/slab: Support disabling SLAB_BUCKETS at boot Chris Down
2026-10-31  4:17   ` Kees Cook
2026-11-01 18:34     ` Harry Yoo
2026-11-13  8:52       ` Chris Down
2026-11-13  8:51     ` Chris Down
2026-10-29  6:08 ` [PATCH v2 4/6] slub_kunit: Add a test for the slab_buckets boot parameter Chris Down
2026-10-31  4:22   ` Kees Cook
2026-11-13  8:52     ` Chris Down
2026-10-29  6:09 ` [PATCH v2 5/6] mm/slab: Support disabling KMALLOC_PARTITION_CACHES at boot Chris Down
2026-10-31  4:28   ` Kees Cook
2026-11-13  8:52     ` Chris Down
2026-10-29  6:09 ` [PATCH v2 6/6] slub_kunit: Add a test for the kmalloc_partition boot parameter Chris Down
2026-10-31  4:29   ` Kees Cook

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