From patchwork Thu Nov 21 18:15:17 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 11256783 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 1CE0E14DB for ; Thu, 21 Nov 2019 18:15:51 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 417B7206CC for ; Thu, 21 Nov 2019 18:15:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="nANVur5k" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 417B7206CC 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-17415-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 30200 invoked by uid 550); 21 Nov 2019 18:15:43 -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: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 29993 invoked from network); 21 Nov 2019 18:15:41 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=ccHak5xmnouFPda/AWVo/lGwU/xGWHbS5K0BgsHuUQE=; b=nANVur5kLJlbf+6u+7VUDkKEjaiMC2PFH5e24iCf0pYkdwHtQD0NWweCruV4r8kb3e CcjwoSrV0Dgahhol5DLONFuh3LbyzNHH/0qWrI0YQ6vdFVp6rmeUdhnvVjKuUR2ff46N 6iIMYjQf4aJWK8+XkAl07Qtt4SskGL3F5TRZU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=ccHak5xmnouFPda/AWVo/lGwU/xGWHbS5K0BgsHuUQE=; b=alSDSixBRJB38ANaK4SCKzJlYXftD8pgAwcY6C2NLYZE8fYmroezvttdViu7Hy9a1v HbzIGltVJt51ftd8vVbdUHFabtwnoya2qlpIc8xMckAX3lcFIcXv4lL+3b7sxQ4m8E7V WuDfwDCg3JBZYyQp686SqXpHadNaXIxX37eG6lg89SfmT2MzGpI+oWOUKhMuGVKuWWVe ivH0FBfAHSuohmBf7XNsOr/tG7SwmsPJaJqBj19acx+xcXR5z6JKSRQyYkw079PwB49X CVtktBxOABBwWeXTl5YZXxQtxCJKpcLAFM1+FXe7lap11/DwB0sdLxqG6psZ5ubFids0 82sg== X-Gm-Message-State: APjAAAUqrWTiTxhWiRLOtl2xgIM0Hxd0wgKXsQxcT38sD7wQDbLFOop9 8t27GEvuV6p6BzEXLIiNQFnetw== X-Google-Smtp-Source: APXvYqxBltaVztxF8obBvw++HqCE/1IaQdeMeweeYTlarHq2vfh1pumYJ2FFNKeqzOLaoVxRGNOQMw== X-Received: by 2002:a63:535c:: with SMTP id t28mr11108812pgl.173.1574360129873; Thu, 21 Nov 2019 10:15:29 -0800 (PST) From: Kees Cook To: Andrew Morton Cc: Kees Cook , 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: [PATCH v2 1/3] ubsan: Add trap instrumentation option Date: Thu, 21 Nov 2019 10:15:17 -0800 Message-Id: <20191121181519.28637-2-keescook@chromium.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191121181519.28637-1-keescook@chromium.org> References: <20191121181519.28637-1-keescook@chromium.org> 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. config UBSAN_SANITIZE_ALL bool "Enable instrumentation for the entire kernel" diff --git a/lib/Makefile b/lib/Makefile index c5892807e06f..bc498bf0f52d 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -272,7 +272,9 @@ quiet_cmd_build_OID_registry = GEN $@ clean-files += oid_registry_data.c obj-$(CONFIG_UCS2_STRING) += ucs2_string.o +ifneq ($(CONFIG_UBSAN_TRAP),y) obj-$(CONFIG_UBSAN) += ubsan.o +endif UBSAN_SANITIZE_ubsan.o := n KASAN_SANITIZE_ubsan.o := n diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan index 019771b845c5..668a91510bfe 100644 --- a/scripts/Makefile.ubsan +++ b/scripts/Makefile.ubsan @@ -1,5 +1,10 @@ # SPDX-License-Identifier: GPL-2.0 ifdef CONFIG_UBSAN + +ifdef CONFIG_UBSAN_ALIGNMENT + CFLAGS_UBSAN += $(call cc-option, -fsanitize=alignment) +endif + CFLAGS_UBSAN += $(call cc-option, -fsanitize=shift) CFLAGS_UBSAN += $(call cc-option, -fsanitize=integer-divide-by-zero) CFLAGS_UBSAN += $(call cc-option, -fsanitize=unreachable) @@ -9,8 +14,8 @@ ifdef CONFIG_UBSAN CFLAGS_UBSAN += $(call cc-option, -fsanitize=bool) CFLAGS_UBSAN += $(call cc-option, -fsanitize=enum) -ifdef CONFIG_UBSAN_ALIGNMENT - CFLAGS_UBSAN += $(call cc-option, -fsanitize=alignment) +ifdef CONFIG_UBSAN_TRAP + CFLAGS_UBSAN += $(call cc-option, -fsanitize-undefined-trap-on-error) endif # -fsanitize=* options makes GCC less smart than usual and