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 X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DE14C2BA2B for ; Tue, 14 Apr 2020 02:40:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7871D2076B for ; Tue, 14 Apr 2020 02:40:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586832029; bh=GNvS7SjQhIauNod0k4pC6jzO5legdDRK81u6znWCNG8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=AaHUPfnU1mqU4NAgJD8fihAKLXLoKwGhmF6sxYbcG1ynAB53jkKEbNSEidKnV+cua a27zmo3AyPo/BOVvQZSK/Qs1pzvt7Gku6H/giPDIady9jEERMZkoTtpN4oMvJmK0iv 5ZraDfXkKC0Z4Ma7RRP0BpCkr5MHJOmB8rBgt1qU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404148AbgDNCk2 (ORCPT ); Mon, 13 Apr 2020 22:40:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:56188 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728736AbgDNCk2 (ORCPT ); Mon, 13 Apr 2020 22:40:28 -0400 Received: from localhost (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0D67F2075E; Tue, 14 Apr 2020 02:40:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586832027; bh=GNvS7SjQhIauNod0k4pC6jzO5legdDRK81u6znWCNG8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=zsBhgUn5DQwZQi7V9qXVoO19WQvaDUXMalfayuwLePLFH7/zlWdgH4RVStxGgh1br smlheOJAR3vhkGg8dUfi0/yxO/ipvCTzX3sllQXmF3IRp0LYCWgYGnSaJTqE/ztWQM 8aTalUJ9NH9Pu/ABZ6XQmwJmjbsGubhhxeMMZEac= Date: Mon, 13 Apr 2020 22:40:25 -0400 From: Sasha Levin To: gregkh@linuxfoundation.org Cc: keescook@chromium.org, akpm@linux-foundation.org, cl@linux.com, iamjoonsoo.kim@lge.com, penberg@kernel.org, rientjes@google.com, silvio.cesare@gmail.com, stable@vger.kernel.org, torvalds@linux-foundation.org Subject: Re: FAILED: patch "[PATCH] slub: improve bit diffusion for freelist ptr obfuscation" failed to apply to 4.19-stable tree Message-ID: <20200414024025.GC1068@sasha-vm> References: <1586506142226229@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <1586506142226229@kroah.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Fri, Apr 10, 2020 at 10:09:02AM +0200, gregkh@linuxfoundation.org wrote: > >The patch below does not apply to the 4.19-stable tree. >If someone wants it applied there, or to any other stable or longterm >tree, then please email the backport, including the original git commit >id to . > >thanks, > >greg k-h > >------------------ original commit in Linus's tree ------------------ > >>From 1ad53d9fa3f6168ebcf48a50e08b170432da2257 Mon Sep 17 00:00:00 2001 >From: Kees Cook >Date: Wed, 1 Apr 2020 21:04:23 -0700 >Subject: [PATCH] slub: improve bit diffusion for freelist ptr obfuscation > >Under CONFIG_SLAB_FREELIST_HARDENED=y, the obfuscation was relatively weak >in that the ptr and ptr address were usually so close that the first XOR >would result in an almost entirely 0-byte value[1], leaving most of the >"secret" number ultimately being stored after the third XOR. A single >blind memory content exposure of the freelist was generally sufficient to >learn the secret. > >Add a swab() call to mix bits a little more. This is a cheap way (1 >cycle) to make attacks need more than a single exposure to learn the >secret (or to know _where_ the exposure is in memory). > >kmalloc-32 freelist walk, before: > >ptr ptr_addr stored value secret >ffff90c22e019020@ffff90c22e019000 is 86528eb656b3b5bd (86528eb656b3b59d) >ffff90c22e019040@ffff90c22e019020 is 86528eb656b3b5fd (86528eb656b3b59d) >ffff90c22e019060@ffff90c22e019040 is 86528eb656b3b5bd (86528eb656b3b59d) >ffff90c22e019080@ffff90c22e019060 is 86528eb656b3b57d (86528eb656b3b59d) >ffff90c22e0190a0@ffff90c22e019080 is 86528eb656b3b5bd (86528eb656b3b59d) >... > >after: > >ptr ptr_addr stored value secret >ffff9eed6e019020@ffff9eed6e019000 is 793d1135d52cda42 (86528eb656b3b59d) >ffff9eed6e019040@ffff9eed6e019020 is 593d1135d52cda22 (86528eb656b3b59d) >ffff9eed6e019060@ffff9eed6e019040 is 393d1135d52cda02 (86528eb656b3b59d) >ffff9eed6e019080@ffff9eed6e019060 is 193d1135d52cdae2 (86528eb656b3b59d) >ffff9eed6e0190a0@ffff9eed6e019080 is f93d1135d52cdac2 (86528eb656b3b59d) > >[1] https://blog.infosectcbr.com.au/2020/03/weaknesses-in-linux-kernel-heap.html > >Fixes: 2482ddec670f ("mm: add SLUB free list pointer obfuscation") >Reported-by: Silvio Cesare >Signed-off-by: Kees Cook >Signed-off-by: Andrew Morton >Cc: Christoph Lameter >Cc: Pekka Enberg >Cc: David Rientjes >Cc: Joonsoo Kim >Cc: >Link: http://lkml.kernel.org/r/202003051623.AF4F8CB@keescook >Signed-off-by: Linus Torvalds As previously promised, I've grabbed d5767057c9a7 ("uapi: rename ext2_swab() to swab() and share globally in swab.h") so that we'll have swab() on 4.19 and 4.14, but it wasn't enough. There was another conflict with d36a63a943e3 ("kasan, slub: fix more conflicts with CONFIG_SLAB_FREELIST_HARDENED") which I've resolved by simply doing: diff --git a/mm/slub.c b/mm/slub.c index 958a8f7a3c253..d2db6bc5e788b 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -248,7 +248,7 @@ static inline void *freelist_ptr(const struct kmem_cache *s, void *ptr, unsigned long ptr_addr) { #ifdef CONFIG_SLAB_FREELIST_HARDENED - return (void *)((unsigned long)ptr ^ s->random ^ ptr_addr); + return (void *)swab((unsigned long)ptr ^ s->random ^ ptr_addr); #else return ptr; #endif -- Thanks, Sasha