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R. Silva" , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-hardening@vger.kernel.org, linux-arm-kernel@lists.infradead.org, llvm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] hardening: Refresh KCFI options, add some more Message-ID: <202404301409.D3BC98D5@keescook> References: <20240426222940.work.884-kees@kernel.org> <20240430092140.GE40213@noisy.programming.kicks-ass.net> <202404301037.9E34D4811@keescook> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202404301037.9E34D4811@keescook> On Tue, Apr 30, 2024 at 10:48:36AM -0700, Kees Cook wrote: > On Tue, Apr 30, 2024 at 11:21:40AM +0200, Peter Zijlstra wrote: > > On Fri, Apr 26, 2024 at 03:29:44PM -0700, Kees Cook wrote: > > > > > - CONFIG_CFI_CLANG=y for x86 and arm64. (And disable FINEIBT since > > > it isn't as secure as straight KCFI.) > > > > Oi ? > > Same objection I always had[1]: moving the check into the destination > means attacks with control over executable memory contents can just omit > the check. > > But now that I went to go look I see 0c3e806ec0f9 ("x86/cfi: Add boot > time hash randomization") is only enabled under FINEIBT... seems better > if that were always enabled... And FINEIBT actually can't be disabled... :| And as it turns out CFI_CLANG doesn't work at all on v6.9... [ 0.587220] no CFI hash found at: __call_sites+0x339a8/0x34450 ffffffffac20cef8 00 00 00 00 00 [ 0.588226] WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:1182 __apply_fineibt+0x7a9/0x820 ... [ 0.619220] SMP alternatives: Something went horribly wrong trying to rewrite the CFI implementation. *hang* -- Kees Cook 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DCDEDC4345F for ; Tue, 30 Apr 2024 21:16:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=+N0KOCqi3zD303AQ6qDYwRDeD+bDResS1IW1p9dyomE=; b=mF8bPw216DpkO1 fvEUjivT/cN93rLBhnFbV1HLQArxKqjmcjK0R4v1ksPX7CqcWLIWUgHKebmhO3MOs58qg2PQdkwXQ oCo7pW327RoHaMI+oZ2OsfbtKb0GRSYZPSVqI3yJMkunHVhGnDJ/VGWKax2eUNNG/zm82UzZRjSw2 MsxLrTeOTH1uIPau3ItEf5I0+OO/9dKlSdQh2jlwhRgXNZYW1NeS3x5D7IujCGMYc4VO6TDaJqHks VBpqQetZzzihHJNZ1Ej1jeHnDn2HiE7Zo0cd2UefTz4BxGxHCpKo0PsbAB6Kx7UrtZsbmAAl/1wcQ u94GaKovt63e/a6L5gHA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1s1upX-00000007wxg-3s80; Tue, 30 Apr 2024 21:16:03 +0000 Received: from mail-pl1-x630.google.com ([2607:f8b0:4864:20::630]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1s1upU-00000007wwF-0bh3 for linux-arm-kernel@lists.infradead.org; Tue, 30 Apr 2024 21:16:02 +0000 Received: by mail-pl1-x630.google.com with SMTP id d9443c01a7336-1e834159f40so50525025ad.2 for ; Tue, 30 Apr 2024 14:15:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1714511755; x=1715116555; darn=lists.infradead.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=ybsFpX0X7CRfB780REANsMjNyYm7Y9wsUjgmwPZjU6k=; b=gtVJRr4BZoj8HJw6F9Mby3pZ6it4rvHoygZNUYR2N8cqxpB+qFLL0hJEdIbF1CZH8t czSZE1NNPfkGo1tCn8XFIwMDmeC94vhlh3kGVm0ag8ykxxc2h5INJeJ/V9nd2SfvC1nW 1RnML9IO8c/qWJqI3fwo+Zv0ByyTdt63Nx588= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1714511755; x=1715116555; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=ybsFpX0X7CRfB780REANsMjNyYm7Y9wsUjgmwPZjU6k=; b=elna2Lbj9MGZA4mt5NC524NROQQezG4ECz3MtFKOc8g9Aqd/RUcpYD6sfHfV1fLnK8 2Krrp1XLcgdWQnc6L8HCy9s8gbNKQwq5bayNDJtDWy57djarDrQ4UIn7IzBkWKehS5qe 7ws6nfRpSgC4h1z7i8ggUDaJfpmC2/mcw1vQikSa6iWRBeByDaGviRAhJfYm1G0Y7ZhZ A+JF4h2xpvpwr5oYHp6qndAtQwyApcYwQI9VxxtfJ0b5spTupBnER1vgl5rBFYjh0gRB YDkSD4B51bnH7yi2ajFmHF34m5YZKZFgWKHUCQ1vY2JqdLVNrOr+jjmdHIO1m1wEuvQG hy2Q== X-Forwarded-Encrypted: i=1; AJvYcCUmjiL+B22Yd8DZV0ALt2/7Qs544N0NaEERClnSAo09V3T9Q+sr+hBN/i9f/y2IqY5wTu4jDWDB+EN0Ts46JmwxZWnGR0/syua2eEfuRS+i0214iPg= X-Gm-Message-State: AOJu0Yzf7K6Ch4exZ1RadKtvqm6x7hwMRsMy2bdxtKRveDCJqCDL/83b X13i+rGT67Tlnrdeb3fJdPSG5wkBUbMaMmEltIQHks4vmtPrpG3P7619MoMVSA== X-Google-Smtp-Source: AGHT+IH65fhAB52q5SRM6fEv53OUPrvdI7HGuP4UMAsLKQOmSK4SnZFW69AZXJZQZh3NFJXh2vI83Q== X-Received: by 2002:a17:902:82c9:b0:1ea:42d1:1421 with SMTP id u9-20020a17090282c900b001ea42d11421mr548705plz.68.1714511754804; Tue, 30 Apr 2024 14:15:54 -0700 (PDT) Received: from www.outflux.net ([198.0.35.241]) by smtp.gmail.com with ESMTPSA id w19-20020a1709027b9300b001e435fa2521sm22879566pll.249.2024.04.30.14.15.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Apr 2024 14:15:54 -0700 (PDT) Date: Tue, 30 Apr 2024 14:15:53 -0700 From: Kees Cook To: Peter Zijlstra Cc: "Gustavo A. R. Silva" , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-hardening@vger.kernel.org, linux-arm-kernel@lists.infradead.org, llvm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] hardening: Refresh KCFI options, add some more Message-ID: <202404301409.D3BC98D5@keescook> References: <20240426222940.work.884-kees@kernel.org> <20240430092140.GE40213@noisy.programming.kicks-ass.net> <202404301037.9E34D4811@keescook> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <202404301037.9E34D4811@keescook> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240430_141600_425375_1A593173 X-CRM114-Status: GOOD ( 18.46 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Apr 30, 2024 at 10:48:36AM -0700, Kees Cook wrote: > On Tue, Apr 30, 2024 at 11:21:40AM +0200, Peter Zijlstra wrote: > > On Fri, Apr 26, 2024 at 03:29:44PM -0700, Kees Cook wrote: > > > > > - CONFIG_CFI_CLANG=y for x86 and arm64. (And disable FINEIBT since > > > it isn't as secure as straight KCFI.) > > > > Oi ? > > Same objection I always had[1]: moving the check into the destination > means attacks with control over executable memory contents can just omit > the check. > > But now that I went to go look I see 0c3e806ec0f9 ("x86/cfi: Add boot > time hash randomization") is only enabled under FINEIBT... seems better > if that were always enabled... And FINEIBT actually can't be disabled... :| And as it turns out CFI_CLANG doesn't work at all on v6.9... [ 0.587220] no CFI hash found at: __call_sites+0x339a8/0x34450 ffffffffac20cef8 00 00 00 00 00 [ 0.588226] WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:1182 __apply_fineibt+0x7a9/0x820 ... [ 0.619220] SMP alternatives: Something went horribly wrong trying to rewrite the CFI implementation. *hang* -- Kees Cook _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel