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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 80091C2BA19 for ; Tue, 14 Apr 2020 08:09:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5BBD72072D for ; Tue, 14 Apr 2020 08:09:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586851782; bh=nWpTxhifAvUKOBH6YVHL1byP+1civbHPAT2oVawRwWw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=eYurCTY892tXfoQbX8W/0H6vx2Ov5yQwps+Vnc6Oxe9K0sYF1qelF9ki8Gwq260U3 Mhlfe05cImBmWTj7zhTFTvX/nEKucjsKB89e40LmQGu+Vg5T1k6hZKzcKkLGMJeyzZ kiSZcCNMfl8UmxiytnJvjKukoR8TiSf5BYJnPn04= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406997AbgDNIJk (ORCPT ); Tue, 14 Apr 2020 04:09:40 -0400 Received: from mail.kernel.org ([198.145.29.99]:52162 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2406984AbgDNIJe (ORCPT ); Tue, 14 Apr 2020 04:09:34 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 EA3802074D; Tue, 14 Apr 2020 08:09:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586851773; bh=nWpTxhifAvUKOBH6YVHL1byP+1civbHPAT2oVawRwWw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=vQ00FOlEHAEZZr0eLZaX3+jo+7QJv3YHb0sdmLx/9R3wf4ccFsNs2A9phF5elEKzB XdttF8ABJAJ23a/j2lgvE/r6pJZkC5tV+YlZiqKaWRX+e9MQB63KSDjyWHyk6ZVAks 6IUfY/RjTDekDK/K7Yohr8ddpoRj2CQJRO6mVSXk= Date: Tue, 14 Apr 2020 10:09:31 +0200 From: Greg KH To: Kees Cook Cc: Sasha Levin , 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: <20200414080931.GB4147420@kroah.com> References: <1586506142226229@kroah.com> <20200414024025.GC1068@sasha-vm> <202004132221.B4CC36F@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202004132221.B4CC36F@keescook> Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Mon, Apr 13, 2020 at 10:24:06PM -0700, Kees Cook wrote: > On Mon, Apr 13, 2020 at 10:40:25PM -0400, Sasha Levin wrote: > > 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); > > Eeek, no, no. The swab() must be on ptr_addr. I already sent a backport > for this to stable, see: > https://lore.kernel.org/stable/202004131001.20346EB0E7@keescook > > Please use that instead. I've dropped Sasha's backport and grabbed yours instead, thanks. greg k-h