From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 423CCCD6E7C for ; Fri, 5 Jun 2026 18:09:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id ABBE36B0092; Fri, 5 Jun 2026 14:09:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A92986B0093; Fri, 5 Jun 2026 14:09:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9D0D46B0095; Fri, 5 Jun 2026 14:09:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 8DFF16B0092 for ; Fri, 5 Jun 2026 14:09:30 -0400 (EDT) Received: from smtpin21.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 5924E1C11DE for ; Fri, 5 Jun 2026 18:09:30 +0000 (UTC) X-FDA: 84846646500.21.3C1EBAE Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf13.hostedemail.com (Postfix) with ESMTP id BE4592000D for ; Fri, 5 Jun 2026 18:09:28 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=MwmqoBT+; spf=pass (imf13.hostedemail.com: domain of kees@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=kees@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1780682968; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=8okm4VUMmFJ4/uejS+xBY+U1Zy2pD+88GtZ8JFsDLIM=; b=Fpv8KvdFN5WdFOohhzCzwvn8pTSXXigfbGmElf512Mo1Bw1q1i72RnUMasdAiV4JaevQ9y 0Z1UmRf4e8BYmw4NSmJe9UkdnPR66E/d/MgjKvBU7QAvm8icyrt1OUCl+WuXzg9T1rfvxe XwwFcAE7xOEnd6UVjhwZELrEaXxX8U4= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1780682968; b=o9pO8Fg/d/dUwy7jYyHMYSBQZVK6DYw+VXfa3Br1/Xt3p/fXWtwjkEUTdGX4S6lXIs2gVv t9EvBblgBAh8kA8WGOPZgOvYNucsILEnw0UDwsUkd4Qhfmp4vw/zy6o7d03sf2vUEoClnd x/QBffRlw9coqC6ke0bPKsYN2HPJ5s8= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=MwmqoBT+; spf=pass (imf13.hostedemail.com: domain of kees@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=kees@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 5EF6B601E3; Fri, 5 Jun 2026 18:09:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 10EFB1F00893; Fri, 5 Jun 2026 18:09:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780682968; bh=8okm4VUMmFJ4/uejS+xBY+U1Zy2pD+88GtZ8JFsDLIM=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=MwmqoBT+H6jm/37A2qDJ0pEvRL2HUAWJWBAOtUi8ZhWYcsigeKif7D+soGUArDr1C cguRomnrcHgH8MS6NkWAdpaw4YL3J0DwUe+7N5eFgkGmrEZ/OYCT0l2tOWSThcJQiq kKwQYZRbaXI0k91YV3ZTa0Dx2V/6Tf5Hu7br6LAK9pmupKtKa2/nLiQjHaCDrtBCMj auFVPz1zVR5Csbvus1K029GUxFmfsvP01zQLtYkAonNOkyfOU+vG04tKBKTAU6cEqV BlKWB2y0+WhmZrVriKbyvcwQtaoGlc/xQMaJ72gzFJzON58dyJ09yaTxRMGlvIOF0f I3rhRblEHkIww== Date: Fri, 5 Jun 2026 11:09:27 -0700 From: Kees Cook To: Pedro Falcato Cc: Vlastimil Babka , Harry Yoo , Andrew Morton , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-hardening@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Simon Horman , Jason Xing , Kuniyuki Iwashima Subject: Re: [PATCH 2/2] net: skb: isolate skb data area allocations into a separate bucket Message-ID: <202606051109.C96C81E3C@keescook> References: <20260602183122.747759-1-pfalcato@suse.de> <20260602183122.747759-3-pfalcato@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260602183122.747759-3-pfalcato@suse.de> X-Rspamd-Queue-Id: BE4592000D X-Rspam-User: X-Stat-Signature: ek1dejkfznnd8798or5ych5ou6xnjrij X-Rspamd-Server: rspam08 X-HE-Tag: 1780682968-749910 X-HE-Meta: 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 lY5uAo9A CSowJM+LPXtqrQQa8sk2Umh9nT/PCN4aSzNhsqkLbYcjwSRIkwfj0JPSNDgkh7FRN6aRoXkrAQkepHW0vw6y0sTXX1vGSySV4f2ywyMXppYSxH06R6yKhu9XB26zBQelokSGBphaHSJrEbw+Rw8sAglKufL2VxRU66BDv79ilQ5bclAzlJwaL7pNYn/HMTtAmCCowbdRQmKb9/MD1eKgFOt+UDxOndtteGEZGJRnjx3Xby6keKQVzTJL4k/MXDNb62e3iAbzvsaIxpYQHmM+hhmvWf2PO5pqEbJz33YEmX4lJHOZ5tqrYmzOyap7QHFDammB6IDnxAn1owsWGATCrGcuTyA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jun 02, 2026 at 07:31:22PM +0100, Pedro Falcato wrote: > SKB data area allocations (as done from alloc_skb()) use kmalloc(). > These allocations can be variably sized and their contents can be more > or less controlled from userspace, which makes them useful for attackers > that want to overwrite a use-after-free'd object from the same kmalloc slab > (which often just requires the sizes to roughly match into the same kmalloc > bucket). [0] is an easy example of an exploit that uses netlink skb > allocation to target another similarly-sized accidentally freed object. > > While other mitigations like CONFIG_RANDOM_KMALLOC_CACHES exist, these are > probabilistic. Use the existing kmem buckets API to further isolate these > allocations in a guaranteed fashion, when CONFIG_SLAB_BUCKETS=y. > > Link: https://github.com/google/security-research/blob/master/pocs/linux/kernelctf/CVE-2023-4207_lts_cos_mitigation_2/docs/exploit.md [0] > Signed-off-by: Pedro Falcato Great! This is exactly what the bucket API was made for. :) Reviewed-by: Kees Cook -- Kees Cook