From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f170.google.com (mail-pg1-f170.google.com [209.85.215.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CF81B15A4 for ; Sat, 24 Feb 2024 01:01:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708736486; cv=none; b=EsVs2CeftJJygBBarlDpF8Na5ikOi8YBjzM/ljOxh4GvjtJit9pZUwTPQYxfSJyC1HzC2Y6A22wylb8qAkR+igm46cttP8dq/fOr6EXjF6qhuNR6NavkRWrbQK4AtO3hrTaT/3V2h8PYxXpnPT2YulaT99v7qwzASYQZdc7tJPk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708736486; c=relaxed/simple; bh=K+YWxm3ZnA65N6uzvESG36jAKxg1RHhLnGwcPKoEkUo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=qhI2IV0hrONAO6lmLsAq1pvL43/pI91maY6Lfzsn7SuS/0W6wnbiWChx2m4TAzFI9vys1BNmApBmNajCeKhVbyNsNYDI9mp4rfCUltPtGvzf0dPd29V3nEarmkEogGbr/64ovZ8yIgasEnku+et/D95ICG5QvwOZDlX0P4RH9fE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org; spf=pass smtp.mailfrom=chromium.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b=e8NzR+3F; arc=none smtp.client-ip=209.85.215.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=chromium.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="e8NzR+3F" Received: by mail-pg1-f170.google.com with SMTP id 41be03b00d2f7-5d3912c9a83so1057403a12.3 for ; Fri, 23 Feb 2024 17:01:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1708736484; x=1709341284; darn=vger.kernel.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=DRLwM6QENBYo07bvqNRkIhBVin7jRxajehNcXch+bs4=; b=e8NzR+3FJP72fLHPIUoJZxSd/2svcOlFZjOI9737xBHqIIKFTGC/vqzbkpLtRkHlZB CBhNAUNralXCpV2B4K8ObspOoXMhzMLJKmM3fn9qZImwpokvNvYm5k+gvj2+s2WtQN8U OOwbY3jURKIO4cb1b6Spwc7LcQE7hh1gxN9tA= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708736484; x=1709341284; 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=DRLwM6QENBYo07bvqNRkIhBVin7jRxajehNcXch+bs4=; b=pAcFMQcZa6T3tObrjuhLyYdYHULEWD3Q2ABbFQzOVLD+EeySdwwDMAAtC9rHsstSjC NHq49hEaCLSYVgMQKt9PrVAhkNTFSOWzI4F6kl6zgqWgLi3//+qVViTloWn7gBsLGy42 mGxijJ/jSucnfAwufdTHLBztxlj4h5jdtyiMSuo3PSHRN23SgXXjuDksVXB8nbTVvfDf Bv1obWas9oCSqhHjKqni1EeeDyEa99/lT2RwnES7zWhvcLlvXqDln1bBHU1p8eScW7xC aJHILIeut9qwcIEC3io3PbxQRapVwwuUzKWADtuBOcYqd+AuVqKvX+Bg7xnB0jKdPyG5 UQXg== X-Forwarded-Encrypted: i=1; AJvYcCW6eMJfsXe1tWDITdlBLrEMlwi373wmpv6eR+bvtsr0PJF6Jk6HjcexTJWKZnpIrr954qvhckfoKnkw+lkk403sZBWDH3s+eCOA3o/D X-Gm-Message-State: AOJu0Yzos/Cb5F/xb7B6deGaEHtULElAo2fCKbLXyswcvfSpmBzpfDY4 cQQgkiVZ/kHB86zSFs10Nl87fxE2ddPJrCsHnwy9p0hUbC4VA/ylQpPenONjSw== X-Google-Smtp-Source: AGHT+IEQ/boZR0NbbEtoiMOkLTe3Imh3KOI4GOUbKXTvlWKbMxa6XhC6hM+HIa944+irNktavkW2SA== X-Received: by 2002:a05:6a21:8ccc:b0:19e:c777:5c6c with SMTP id ta12-20020a056a218ccc00b0019ec7775c6cmr1727576pzb.19.1708736482583; Fri, 23 Feb 2024 17:01:22 -0800 (PST) Received: from www.outflux.net ([198.0.35.241]) by smtp.gmail.com with ESMTPSA id y5-20020a62b505000000b006e0447d48b0sm90582pfe.23.2024.02.23.17.01.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Feb 2024 17:01:22 -0800 (PST) Date: Fri, 23 Feb 2024 17:01:21 -0800 From: Kees Cook To: Dmitry Vyukov Cc: Kostya Serebryany , Vitaly Buka , glider@google.com, Evgeniy Stepanov , Daniel Micay , Catalin Marinas , Will Deacon , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Pratyush Anand , Dong Bo , Dmitry Safonov , Rik van Riel , Andy Lutomirski , Grzegorz Andrejczuk , linux-arm-kernel@lists.infradead.org, Reid Kleckner , Andrew Morton , Peter Collingbourne , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, address-sanitizer@googlegroups.com Subject: Re: [PATCH] mm: Revert x86_64 and arm64 ELF_ET_DYN_BASE base Message-ID: <202402231649.086D1A3A@keescook> References: <20170807201542.GA21271@beast> <202402162238.E5D08F5968@keescook> Precedence: bulk X-Mailing-List: linux-kernel@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: On Tue, Feb 20, 2024 at 08:47:09AM +0100, Dmitry Vyukov wrote: > On Sat, 17 Feb 2024 at 07:50, Kees Cook wrote: > > > > *extreme thread[1] necromancy* > > > > On Mon, Aug 07, 2017 at 01:15:42PM -0700, Kees Cook wrote: > > > Moving the x86_64 and arm64 PIE base from 0x555555554000 to 0x000100000000 > > > broke AddressSanitizer. This is a partial revert of: > > > > > > commit eab09532d400 ("binfmt_elf: use ELF_ET_DYN_BASE only for PIE") > > > commit 02445990a96e ("arm64: move ELF_ET_DYN_BASE to 4GB / 4MB") > > > > > > The AddressSanitizer tool has hard-coded expectations about where > > > executable mappings are loaded. The motivation for changing the PIE > > > base in the above commits was to avoid the Stack-Clash CVEs that > > > allowed executable mappings to get too close to heap and stack. This > > > was mainly a problem on 32-bit, but the 64-bit bases were moved too, > > > in an effort to proactively protect those systems (proofs of concept > > > do exist that show 64-bit collisions, but other recent changes to fix > > > stack accounting and setuid behaviors will minimize the impact). > > > > I happened to be looking at this again today, and wondered where things > > stood. It seems like ASan's mappings are documented here: > > https://github.com/google/sanitizers/wiki/AddressSanitizerAlgorithm#64-bit > > > > This implies that it would be safe to move the ELF_ET_DYN_BASE from > > 0x555555554000 down to 0x200000000000, since the shadow map ends at > > 0x10007fff7fff. (Well, anything above there would work, I was just > > picking a "round" number above it. We could just as well use > > 0x100080000000, I think.) > > > > Is this correct? I'd like to open up some more room between mmap and > > stack... Thanks for the details! > Note that there is also TSAN and MSAN with their own mappings. > These are also different per-arch, e.g. TSAN/Linux/x86_64: > https://github.com/llvm/llvm-project/blob/d2a26a7bd5fc7cc5752337b7f4f999642feb37dc/compiler-rt/lib/tsan/rtl/tsan_platform.h#L48-L58 > Search "linux/" in that file for other arches, e.g.: > https://github.com/llvm/llvm-project/blob/d2a26a7bd5fc7cc5752337b7f4f999642feb37dc/compiler-rt/lib/tsan/rtl/tsan_platform.h#L156-L165 > https://github.com/llvm/llvm-project/blob/d2a26a7bd5fc7cc5752337b7f4f999642feb37dc/compiler-rt/lib/tsan/rtl/tsan_platform.h#L187-L196 > https://github.com/llvm/llvm-project/blob/d2a26a7bd5fc7cc5752337b7f4f999642feb37dc/compiler-rt/lib/tsan/rtl/tsan_platform.h#L218-L227 > https://github.com/llvm/llvm-project/blob/d2a26a7bd5fc7cc5752337b7f4f999642feb37dc/compiler-rt/lib/tsan/rtl/tsan_platform.h#L252-L263 Depending on VA size, these are effectively all below 0x3800 0000 0000. > > And MSAN mappings: > https://github.com/llvm/llvm-project/blob/d2a26a7bd5fc7cc5752337b7f4f999642feb37dc/compiler-rt/lib/msan/msan.h#L44-L61 These are all below 0x1000 0000 0000. So there probably isn't much benefit in reducing the PIE program position below the current 0x55.... Okay, thanks! -- Kees Cook