From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793420011; b=zmugZ1x5HZFIum+ahIqj6xMpIkNRzsrJ/Qa7f05BIn2HBA0TwRX1SepDWSa0R0HDEgVM XvVyvPDqp9BIKqRmpoj137RW2fZeONjC12S/4DasWh40GW5nEjuoYgzTXFrsIGmfo9H4J xLgivU3oVkD9s2q9nduVqnQTH8tGhUxw6UPBICSswivZQ07ELzsjKEjoO7mUc3Tie5rxz A8rmMxVxxUtwQta33PN3DPyBLBhrzRbqP9kcybfY7r0qJGL9ZhG/F1u3jKKY+fj4z31Bx h3AgNtWe2fOp+uf0PVy3b+VM/g7hvlnFLHw+QOb/CvPpcmvCMz0T7SZ9zgXNr1K+gtg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793420011; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition:In-Reply-To; bh=3hdblefE6S5tAiJMj8KJmoICUKdholikSnOmEf5tzMU=; b=X0v/rwl/LIsLamJ1pshdNn66YI2oDkeGBminXiC5f3+GHN4Hb311Aui8qR2h+OqgvA8l UfUUZrf2brW9QzR1WEkIfw8hXSKGbRlHTTNSz5vswVxwiClEa0H19++P/5eGLZwUjic3N rpN2gH6QZzWRQHtMbPylwGwXgjje2Vg+EXW135//kJa7CArEt2WAwlwvAWmA92ULhqNr0 fe0jQtEmeXKTqGn0OlKZHe5CnPJmrHeNpuZ4j8xtEJXzFqOsWgotAXdRLzuOawlf4zQ2p B12tFhWDvRDv0d6miZX8wFF12jW9kaaeWOVHk336WrRhdPK42Ik1i9UefGk20mNhGlg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=R4EQdXBN; 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 7F569606A31A; Sat, 31 Oct 2026 04:13:31 +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=R4EQdXBN Received: by smtp.kernel.org (Postfix) with ESMTPSA id 04F601F000C1; Sat, 31 Oct 2026 04:13:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793420011; bh=3hdblefE6S5tAiJMj8KJmoICUKdholikSnOmEf5tzMU=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=R4EQdXBNX8QLXGc0X8TmBH9Fb9wWbqf+Oyh7f7jwj4AQpxv0TaRTM+7oBwtj9pXcT kufcOzg4jPz6GRNP+iX6tFOWBfsU1mAYaGgqHYG2KRsiM14/+4ZLjO7CJBikdSMBpJ wVkiA3Y5wG7dEInpGmZFZ2JLXRYrEJFIGjxAMD5eqBw8yBcxEEyJxPAfr+XSZE/98X 0AwNwjGi479VRMBjZkIVFsZ8kiCCML/MQmWVQtHlS9ylY4ZS1f21kzS1cLumk073Lw Ve0mbW/MPWGakjeHzDS4YCtvvKb4rP50KyXWyYkP0gtn7AIbRYA/mJFlm4a2Soau1B EBx8vWbmq8Zmg== Date: Fri, 30 Oct 2026 21:13:30 -0700 From: Kees Cook To: Chris Down Cc: Vlastimil Babka , Harry Yoo , Andrew Morton , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Marco Elver , GONG Ruiqi , 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 Subject: Re: [PATCH v2 1/6] mm/slab: Enable SLAB_FREELIST_HARDENED by default Message-ID: <202610302112.453CE16119@keescook> References: <2ba9dc862607d70050bbc86fce0091de2e23c023.1793253633.git.chris@chrisdown.name> X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2ba9dc862607d70050bbc86fce0091de2e23c023.1793253633.git.chris@chrisdown.name> On Thu, Oct 29, 2026 at 02:07:22PM +0800, Chris Down wrote: > SLAB_FREELIST_HARDENED obfuscates the free pointers stored in free > objects, and catches naive double frees and frees to the wrong cache. > Most distros already enable it, and with sheaves its cost is small, > since the per-cpu fast paths don't touch freelists. Measurements also > show this quite clearly [1][2]. > > So let's just enable it by default. SLAB_BUCKETS defaults to > SLAB_FREELIST_HARDENED, so it's now enabled by default too. > > Link: https://lore.kernel.org/all/auITixAJMfLtfa7i@chrisdown.name/ [1] > Link: https://lore.kernel.org/all/179312451613.474906.1475329637924619088@kernel.org/ [2] > Suggested-by: Vlastimil Babka > Signed-off-by: Chris Down Like I've always wanted it. :) Reviewed-by: Kees Cook -- Kees Cook