From patchwork Thu Apr 2 04:04:23 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 11469845 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B1BA615AB for ; Thu, 2 Apr 2020 04:04:26 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7E8082074D for ; Thu, 2 Apr 2020 04:04:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="X+z7Cdd9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7E8082074D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 7EBBA8E000C; Thu, 2 Apr 2020 00:04:25 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 79D9C8E0007; Thu, 2 Apr 2020 00:04:25 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6D8B38E000C; Thu, 2 Apr 2020 00:04:25 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0159.hostedemail.com [216.40.44.159]) by kanga.kvack.org (Postfix) with ESMTP id 55B818E0007 for ; Thu, 2 Apr 2020 00:04:25 -0400 (EDT) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 1A091181AC9CC for ; Thu, 2 Apr 2020 04:04:25 +0000 (UTC) X-FDA: 76661572890.12.name46_26885b5a9c35f X-Spam-Summary: 50,0,0,767f05756c679743,d41d8cd98f00b204,akpm@linux-foundation.org,,RULES_HIT:41:355:379:800:960:965:966:967:973:988:989:1260:1263:1345:1359:1381:1431:1437:1534:1542:1711:1730:1747:1777:1792:2196:2197:2199:2200:2393:2525:2560:2564:2682:2685:2739:2859:2902:2933:2937:2939:2942:2945:2947:2951:2954:3000:3022:3138:3139:3140:3141:3142:3353:3865:3866:3867:3868:3870:3871:3874:3934:3936:3938:3941:3944:3947:3950:3953:3956:3959:4250:4321:4385:4390:4395:4605:5007:6117:6119:6120:6261:6653:6691:6737:7514:7576:7901:7903:8599:8660:9010:9025:9121:9545:10004:10913:11026:11473:11658:11914:12043:12048:12297:12438:12517:12519:12555:12679:12783:12903:12986:13148:13221:13229:13230:14181:14721:14849:21080:21220:21451:21611:21627:21939:21990:30003:30034:30054,0,RBL:198.145.29.99:@linux-foundation.org:.lbl8.mailshell.net-62.2.0.100 64.100.201.201,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:1,LUA_SUMMAR Y:none X-HE-Tag: name46_26885b5a9c35f X-Filterd-Recvd-Size: 4147 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf05.hostedemail.com (Postfix) with ESMTP for ; Thu, 2 Apr 2020 04:04:24 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (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 7CEBD20747; Thu, 2 Apr 2020 04:04:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585800263; bh=//dpfVJU5xoiTxlZwJWGVZOPbSQ/caf2UDRBtOLemBI=; h=Date:From:To:Subject:In-Reply-To:From; b=X+z7Cdd9VrWY9C9WC6zhaVM5s7lje4yqSxjpYn0WFid+B8YXsUhOEdGrM6+YGaymj y9uDXwN94jsFYsqaFqfNtrjDzmAOMxJIpgHRloTBRxcox3rLx602J5kDaT5ECOKP/r jt4tNhEufNeZWOAyBZlyySIyJcLxwpur7nhLHFQQ= Date: Wed, 01 Apr 2020 21:04:23 -0700 From: Andrew Morton To: akpm@linux-foundation.org, cl@linux.com, iamjoonsoo.kim@lge.com, keescook@chromium.org, linux-mm@kvack.org, mm-commits@vger.kernel.org, penberg@kernel.org, rientjes@google.com, silvio.cesare@gmail.com, stable@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 024/155] slub: improve bit diffusion for freelist ptr obfuscation Message-ID: <20200402040423.oMxgUNpgm%akpm@linux-foundation.org> In-Reply-To: <20200401210155.09e3b9742e1c6e732f5a7250@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Kees Cook Subject: 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 Link: http://lkml.kernel.org/r/202003051623.AF4F8CB@keescook Fixes: 2482ddec670f ("mm: add SLUB free list pointer obfuscation") Reported-by: Silvio Cesare Signed-off-by: Kees Cook Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Signed-off-by: Andrew Morton --- mm/slub.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/slub.c~slub-improve-bit-diffusion-for-freelist-ptr-obfuscation +++ a/mm/slub.c @@ -259,7 +259,7 @@ static inline void *freelist_ptr(const s * freepointer to be restored incorrectly. */ return (void *)((unsigned long)ptr ^ s->random ^ - (unsigned long)kasan_reset_tag((void *)ptr_addr)); + swab((unsigned long)kasan_reset_tag((void *)ptr_addr))); #else return ptr; #endif