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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=OuicXfmk; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 80071606A31F; Tue, 27 Oct 2026 08:10:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=OuicXfmk Received: by smtp.kernel.org (Postfix) with ESMTPSA id B40B41F01828; Tue, 27 Oct 2026 08:10:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793088646; bh=dDmwmjf1rca7vDceLffwmnsnZHqgu7Yv+wtoDgqD3S0=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=OuicXfmkCul7MY0Y5pAoKRjE+HsPz/d6Z5LAZ89V6dhsXZuh0FzVVNsxN7gs2PTli jDlNrVoA78k6uChpYYfdukgoWkhsHGLaW0vhy0jgREaMpxP2TtUShAxOKPl3dv09lk qbbFAs1VA9dN7jtTCl9gKRYPdnFlggSd4augInStF/GhJymAwBnL5iS3vr4bPvps7b lznY+CO12tXwJSxLi/rRnjkt9IQ8Hs9cVByOM/tSGc5ThASptgvVlxYLFV6A5E1RPI 3fjEE+YfMqB906EBk2d1Z0Ruoz6NZuW6IGGpcf15uzuUT6qSUfUwAUjt89VfmHRBCt cdkqL6kErpc5g== Message-ID: <16121542-acd5-4727-b64c-f8d519145b63@kernel.org> Date: Tue, 27 Oct 2026 09:10:40 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/8] mm/slab: Support selecting slab hardening features at boot To: Chris Down , Harry Yoo , Andrew Morton Cc: Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Kees Cook , Marco Elver , GONG Ruiqi , Jan Kiszka , Kieran Bingham , Jonathan Corbet , linux-mm@kvack.org, linux-hardening@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com References: From: "Vlastimil Babka (SUSE)" Content-Language: en-US Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/27/26 08:35, Chris Down wrote: > Slab hardening settings are currently all build time choices. This means > that, unfortunately, hosts with different requirements end up needing > separate kernel images. Let's allow those hosts to use one image and > select each policy at boot instead. > > This series adds four new boot parameters that default to their values > from CONFIG_*: > > slab_freelist_hardened= > slab_freelist_random= These two should be only a small cpu overhead, which is why distros generally enable them [1]. Also the code basically only runs in slowpaths because percpu caching doesn't use freelists. It's possible the static key conversion doesn't help anything. You could try to measure the impact, I'd be surprised perhaps :) Maybe we should just make them default=y. > slab_buckets= > kmalloc_partition= These are more valid as there's a memory overhead tradeoff. [1] https://oracle.github.io/kconfigs/?config=UTS_RELEASE&config=SLAB_FREELIST_RANDOM&config=SLAB_FREELIST_HARDENED > These mostly act at cache initialisation time. For free list hardening we > use a static key settled before the first free pointer is written. > > Chris Down (8): > mm/slub: Support disabling freelist hardening at boot > slub_kunit: Add a test for slab_freelist_hardened= > mm/slub: Support disabling freelist randomisation at boot > slub_kunit: Add a test for slab_freelist_random= > mm/slab: Support disabling SLAB_BUCKETS at boot > slub_kunit: Add a test for the slab_buckets boot parameter > mm/slab: Support disabling KMALLOC_PARTITION_CACHES at boot > slub_kunit: Add a test for the kmalloc_partition boot parameter > > .../admin-guide/kernel-parameters.txt | 29 +++ > lib/tests/slub_kunit.c | 186 ++++++++++++++++++ > mm/Kconfig | 15 ++ > mm/slab.h | 24 +++ > mm/slab_common.c | 48 ++++- > mm/slub.c | 68 ++++++- > scripts/gdb/linux/slab.py | 8 +- > 7 files changed, 361 insertions(+), 17 deletions(-) > > > base-commit: d15d7703166daf7bd62c844a3cb1b3a6279adb4c