From patchwork Thu Feb 27 18:49:17 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 11409511 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 0A4B014B4 for ; Thu, 27 Feb 2020 18:49:48 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id E423B246C6 for ; Thu, 27 Feb 2020 18:49:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="eXruJRfn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E423B246C6 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-17977-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 3734 invoked by uid 550); 27 Feb 2020 18:49:40 -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 3699 invoked from network); 27 Feb 2020 18:49:39 -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 :mime-version:content-transfer-encoding; bh=TZN5E5934TvMDmRyA6YbiUZA3oVW+HYGx9jzlGs1fas=; b=eXruJRfnQmahJDeyOvX95cjw0dXGhTf7PEpDDj6CQlvkVdL87yFHrwKSQm2LixP2lk 8au/afqF+SQ1+SMDz9z/6272yLFXtVIAvGceYi3lt7xxtZw8aDgZpl1SVaFyCKSxRA+E GF5oUviUdxtOaY5AMoMhU870DTHlhwK5HwGJI= 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:mime-version:content-transfer-encoding; bh=TZN5E5934TvMDmRyA6YbiUZA3oVW+HYGx9jzlGs1fas=; b=rDTp1JELHxb6q8RRQA1eRjhrZaL7YgM0IRA2UdAp4dQ9YkXavgtvZC/vZd+GqHkK6m rtYIb3cn3cvE+j7B9+v925XpOlrK+57ExESIl3ODrhnaaihCWyD8THlOvfgki6RzRDcu nSFErJ6cY+SEtwwLx3Pp3Sf7FyhDkHA0C3RFC9DB5JvySaDd5jNuhSPj33VRfl+Dc5K4 kIMgTPg9MmJNMiE1cvhvNREpa3yNHBSSk0sYG7/IZjtvPJ7N3M+f/1k4KoPdm4JYac02 4bHl5d62k7dR5Oy1fINqCc5IDVMH5TOhVX5u4FxOHo0/x7yPy3XsJxYt395mj3B2ACrC xJBA== X-Gm-Message-State: APjAAAUZH1sZ/X8UwEEO6DGt5zjGbCzRgEbpeyW2EDf9bZS8M0iRyE3f cuCbrmqRWbOC5jcSeFyPYNK8Tg== X-Google-Smtp-Source: APXvYqzi0405M2isd5TrmwfjhdAc874OWtUh021IAQSnb+b3v9koU7Y59YGdJnGnP+UkARRMPRwUbQ== X-Received: by 2002:a17:902:8a89:: with SMTP id p9mr160846plo.286.1582829367317; Thu, 27 Feb 2020 10:49:27 -0800 (PST) From: Kees Cook To: Andrew Morton Cc: Kees Cook , Elena Petrova , Andrey Ryabinin , Dmitry Vyukov , Andrey Konovalov , Alexander Potapenko , Dan Carpenter , "Gustavo A. R. Silva" , Arnd Bergmann , Ard Biesheuvel , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, syzkaller@googlegroups.com Subject: [PATCH v4 2/6] ubsan: Split "bounds" checker from other options Date: Thu, 27 Feb 2020 10:49:17 -0800 Message-Id: <20200227184921.30215-3-keescook@chromium.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200227184921.30215-1-keescook@chromium.org> References: <20200227184921.30215-1-keescook@chromium.org> MIME-Version: 1.0 In order to do kernel builds with the bounds checker individually available, introduce CONFIG_UBSAN_BOUNDS, with the remaining options under CONFIG_UBSAN_MISC. For example, using this, we can start to expand the coverage syzkaller is providing. Right now, all of UBSan is disabled for syzbot builds because taken as a whole, it is too noisy. This will let us focus on one feature at a time. For the bounds checker specifically, this provides a mechanism to eliminate an entire class of array overflows with close to zero performance overhead (I cannot measure a difference). In my (mostly) defconfig, enabling bounds checking adds ~4200 checks to the kernel. Performance changes are in the noise, likely due to the branch predictors optimizing for the non-fail path. Some notes on the bounds checker: - it does not instrument {mem,str}*()-family functions, it only instruments direct indexed accesses (e.g. "foo[i]"). Dealing with the {mem,str}*()-family functions is a work-in-progress around CONFIG_FORTIFY_SOURCE[1]. - it ignores flexible array members, including the very old single byte (e.g. "int foo[1];") declarations. (Note that GCC's implementation appears to ignore _all_ trailing arrays, but Clang only ignores empty, 0, and 1 byte arrays[2].) [1] https://github.com/KSPP/linux/issues/6 [2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92589 Suggested-by: Elena Petrova Signed-off-by: Kees Cook Reviewed-by: Andrey Ryabinin Acked-by: Dmitry Vyukov --- lib/Kconfig.ubsan | 29 ++++++++++++++++++++++++----- scripts/Makefile.ubsan | 7 ++++++- 2 files changed, 30 insertions(+), 6 deletions(-) diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan index 9deb655838b0..48469c95d78e 100644 --- a/lib/Kconfig.ubsan +++ b/lib/Kconfig.ubsan @@ -2,7 +2,7 @@ config ARCH_HAS_UBSAN_SANITIZE_ALL bool -config UBSAN +menuconfig UBSAN bool "Undefined behaviour sanity checker" help This option enables the Undefined Behaviour sanity checker. @@ -10,9 +10,10 @@ config UBSAN behaviours at runtime. For more details, see: Documentation/dev-tools/ubsan.rst +if UBSAN + 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 @@ -25,9 +26,26 @@ config UBSAN_TRAP the system. For some system builders this is an acceptable trade-off. +config UBSAN_BOUNDS + bool "Perform array index bounds checking" + default UBSAN + help + This option enables detection of directly indexed out of bounds + array accesses, where the array size is known at compile time. + Note that this does not protect array overflows via bad calls + to the {str,mem}*cpy() family of functions (that is addressed + by CONFIG_FORTIFY_SOURCE). + +config UBSAN_MISC + bool "Enable all other Undefined Behavior sanity checks" + default UBSAN + help + This option enables all sanity checks that don't have their + own Kconfig options. Disable this if you only want to have + individually selected checks. + config UBSAN_SANITIZE_ALL bool "Enable instrumentation for the entire kernel" - depends on UBSAN depends on ARCH_HAS_UBSAN_SANITIZE_ALL # We build with -Wno-maybe-uninitilzed, but we still want to @@ -44,7 +62,6 @@ config UBSAN_SANITIZE_ALL config UBSAN_NO_ALIGNMENT bool "Disable checking of pointers alignment" - depends on UBSAN default y if HAVE_EFFICIENT_UNALIGNED_ACCESS help This option disables the check of unaligned memory accesses. @@ -57,7 +74,9 @@ config UBSAN_ALIGNMENT config TEST_UBSAN tristate "Module for testing for undefined behavior detection" - depends on m && UBSAN + depends on m help This is a test module for UBSAN. It triggers various undefined behavior, and detect it. + +endif # if UBSAN diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan index 668a91510bfe..5b15bc425ec9 100644 --- a/scripts/Makefile.ubsan +++ b/scripts/Makefile.ubsan @@ -5,14 +5,19 @@ ifdef CONFIG_UBSAN_ALIGNMENT CFLAGS_UBSAN += $(call cc-option, -fsanitize=alignment) endif +ifdef CONFIG_UBSAN_BOUNDS + CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds) +endif + +ifdef CONFIG_UBSAN_MISC CFLAGS_UBSAN += $(call cc-option, -fsanitize=shift) CFLAGS_UBSAN += $(call cc-option, -fsanitize=integer-divide-by-zero) CFLAGS_UBSAN += $(call cc-option, -fsanitize=unreachable) CFLAGS_UBSAN += $(call cc-option, -fsanitize=signed-integer-overflow) - CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds) CFLAGS_UBSAN += $(call cc-option, -fsanitize=object-size) CFLAGS_UBSAN += $(call cc-option, -fsanitize=bool) CFLAGS_UBSAN += $(call cc-option, -fsanitize=enum) +endif ifdef CONFIG_UBSAN_TRAP CFLAGS_UBSAN += $(call cc-option, -fsanitize-undefined-trap-on-error)