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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 D57A2C43603 for ; Wed, 18 Dec 2019 00:08:23 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 33BB0218AC for ; Wed, 18 Dec 2019 00:08:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="IHzJ0A0S" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 33BB0218AC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-17506-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 20266 invoked by uid 550); 18 Dec 2019 00:08:17 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 20229 invoked from network); 18 Dec 2019 00:08:16 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=da4hM4UJKgmO9iz3pXI2WshcEvtAp8fX82/geQVC7e0=; b=IHzJ0A0SVCJT2wgdRYnqM2827VaTp+bAXqjahUxWIakErH8H4u3BP8b0EC2opmBBP/ zLgd/VEbimeoyZc9352qbSIanJqf1ICFPxO03lC2eDAprzihhwmC/rgNiFc/JIXuVZ/n jLkjlNMeGdOonrQIV5NUsTbwCMGflwi+FBnOY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=da4hM4UJKgmO9iz3pXI2WshcEvtAp8fX82/geQVC7e0=; b=FcCmwBjbrt7fFFkI+wCoI1lFnMq/5HNxwkLaRwTKDDogeaK+gPfeH2Kshq8qEYlzcD M7nQqFyl9nG6LhI8vXiXfC7F6US6vz3KNnLT5OOpl3gvG+wCjnIBMkLcSPyD0+ZJ8RZV rmLkDAG5zdBXV/SNRQlOLEqBDNqHCV7YA9uYt2NNyDJlv6dv8aC24MjPWKNHlSs/7oeM bV7AquP+TI2Ldy0igussWta2pMIjYmMNOivWkye6cEb12ZwnjzRT4eiTFP/ptkujEqGZ xTkN2l2DlDQnGc4LW80JknJxGNGx8luZ1CeROBEdG6ooa+K8RNlkavcrc/G+X+nOhAnh YIpA== X-Gm-Message-State: APjAAAWTuwlSDcWSutG3BRvrt8kb+E9e96aOzR3qnW2UNX98N/Yw5Im6 UzesLcJ0YxgzAlJ4dTmqHr1PZA== X-Google-Smtp-Source: APXvYqz8C5J4J9eWBQPXjg7+Paw02BtPeFdFGP5+iOGrZw/IMiECgcViQ8/ErKBABJ5diMLnc2/CaA== X-Received: by 2002:aa7:98d0:: with SMTP id e16mr457396pfm.77.1576627684350; Tue, 17 Dec 2019 16:08:04 -0800 (PST) Date: Tue, 17 Dec 2019 16:08:02 -0800 From: Kees Cook To: Will Deacon Cc: Andrew Morton , Andrey Ryabinin , Elena Petrova , Alexander Potapenko , Dmitry Vyukov , Linus Torvalds , Dan Carpenter , "Gustavo A. R. Silva" , Arnd Bergmann , Ard Biesheuvel , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: Re: [PATCH v2 1/3] ubsan: Add trap instrumentation option Message-ID: <201912171607.73EE8133@keescook> References: <20191121181519.28637-1-keescook@chromium.org> <20191121181519.28637-2-keescook@chromium.org> <20191216102655.GA11082@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191216102655.GA11082@willie-the-truck> On Mon, Dec 16, 2019 at 10:26:56AM +0000, Will Deacon wrote: > Hi Kees, > > On Thu, Nov 21, 2019 at 10:15:17AM -0800, Kees Cook wrote: > > The Undefined Behavior Sanitizer can operate in two modes: warning > > reporting mode via lib/ubsan.c handler calls, or trap mode, which uses > > __builtin_trap() as the handler. Using lib/ubsan.c means the kernel > > image is about 5% larger (due to all the debugging text and reporting > > structures to capture details about the warning conditions). Using the > > trap mode, the image size changes are much smaller, though at the loss > > of the "warning only" mode. > > > > In order to give greater flexibility to system builders that want > > minimal changes to image size and are prepared to deal with kernel code > > being aborted and potentially destabilizing the system, this introduces > > CONFIG_UBSAN_TRAP. The resulting image sizes comparison: > > > > text data bss dec hex filename > > 19533663 6183037 18554956 44271656 2a38828 vmlinux.stock > > 19991849 7618513 18874448 46484810 2c54d4a vmlinux.ubsan > > 19712181 6284181 18366540 44362902 2a4ec96 vmlinux.ubsan-trap > > > > CONFIG_UBSAN=y: image +4.8% (text +2.3%, data +18.9%) > > CONFIG_UBSAN_TRAP=y: image +0.2% (text +0.9%, data +1.6%) > > > > Additionally adjusts the CONFIG_UBSAN Kconfig help for clarity and > > removes the mention of non-existing boot param "ubsan_handle". > > > > Suggested-by: Elena Petrova > > Signed-off-by: Kees Cook > > --- > > lib/Kconfig.ubsan | 22 ++++++++++++++++++---- > > lib/Makefile | 2 ++ > > scripts/Makefile.ubsan | 9 +++++++-- > > 3 files changed, 27 insertions(+), 6 deletions(-) > > > > diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan > > index 0e04fcb3ab3d..9deb655838b0 100644 > > --- a/lib/Kconfig.ubsan > > +++ b/lib/Kconfig.ubsan > > @@ -5,11 +5,25 @@ config ARCH_HAS_UBSAN_SANITIZE_ALL > > config UBSAN > > bool "Undefined behaviour sanity checker" > > help > > - This option enables undefined behaviour sanity checker > > + This option enables the Undefined Behaviour sanity checker. > > Compile-time instrumentation is used to detect various undefined > > - behaviours in runtime. Various types of checks may be enabled > > - via boot parameter ubsan_handle > > - (see: Documentation/dev-tools/ubsan.rst). > > + behaviours at runtime. For more details, see: > > + Documentation/dev-tools/ubsan.rst > > + > > +config UBSAN_TRAP > > + bool "On Sanitizer warnings, abort the running kernel code" > > + depends on UBSAN > > + depends on $(cc-option, -fsanitize-undefined-trap-on-error) > > + help > > + Building kernels with Sanitizer features enabled tends to grow > > + the kernel size by around 5%, due to adding all the debugging > > + text on failure paths. To avoid this, Sanitizer instrumentation > > + can just issue a trap. This reduces the kernel size overhead but > > + turns all warnings (including potentially harmless conditions) > > + into full exceptions that abort the running kernel code > > + (regardless of context, locks held, etc), which may destabilize > > + the system. For some system builders this is an acceptable > > + trade-off. > > Slight nit, but I wonder if it would make sense to move all this under a > 'menuconfig UBSAN' entry, so the dependencies can be dropped? Then you could > have all of the suboptions default to on and basically choose which > individual compiler options to disable based on your own preferences. Sure; I can do that. I'll respin the series. -- Kees Cook