From patchwork Thu Nov 21 18:15:18 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 11256789 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 2D50314DB for ; Thu, 21 Nov 2019 18:15:58 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 7AB01206CB for ; Thu, 21 Nov 2019 18:15:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="KrN4zpR8" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7AB01206CB 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-17416-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 30322 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 30035 invoked from network); 21 Nov 2019 18:15:42 -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=JQs/4UxemMcGCjHZn4niB7nA1rMhXtjAz7kJK3AjL7E=; b=KrN4zpR8IEwpUQr4jn2KWwjZqUoeisnx3Am9Bp+lgiRIdx5345vx29iTTUFknjeFFQ Rj9A+pMLGH7kZeXTTYnjwo6xAzbqdCNRhagoYp/K8ogsyNX8Xx9jAt66FmI5COUA2UiY gHkW3zyflbmt4IHuKfJMdE/2YCaQqpLZhk71I= 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=JQs/4UxemMcGCjHZn4niB7nA1rMhXtjAz7kJK3AjL7E=; b=Wlakjf47LX+gtGuiG4YMfrh9EClE+osCBpBQq5BSgqqNDp5i2y78bOt7hu0aN515ut KHWNPGAGHegC5DiaODEYgJ2gts6xfm0XmmFD26dU2VNPaW9lhQoWXKB0xL1Z3v6TRwHs kOy6Wmi5sF7+//LQerHaKIWyl4SclGOEePZGpinP2lyersEhvmGRVV/g0k/qh2BPlv4B aSiYoel5FukYPDYc9OAX2ZiaISWjC8C8VvaHKuTMfbnzvh7aedm9pVGA+ANv1V/dLGCu zAR2C/v3cZRvJnuBAZxM1q82ILczMldRYCnSqB/JKySrGPjVtnS/XJm2CDR/dr677jH8 vO/g== X-Gm-Message-State: APjAAAX1z0FksCX07UtUmZU4V7uskh0lhWVrCc7UKsHhAbQ4u4lszLyE V5Ku3PnPqRHrhxLswzv59MguZw== X-Google-Smtp-Source: APXvYqwbG0mlD3ppkkL3k31yuwYGe/H5GA3+ceT+WKtRCMUFj+fEDoGxidbBeBr46DZ2WJ27O5jcgg== X-Received: by 2002:a65:66c7:: with SMTP id c7mr10861530pgw.407.1574360130724; Thu, 21 Nov 2019 10:15:30 -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 2/3] ubsan: Split "bounds" checker from other options Date: Thu, 21 Nov 2019 10:15:18 -0800 Message-Id: <20191121181519.28637-3-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> 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 --- lib/Kconfig.ubsan | 20 ++++++++++++++++++++ scripts/Makefile.ubsan | 7 ++++++- 2 files changed, 26 insertions(+), 1 deletion(-) diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan index 9deb655838b0..9b9f76d1a3f7 100644 --- a/lib/Kconfig.ubsan +++ b/lib/Kconfig.ubsan @@ -25,6 +25,26 @@ config UBSAN_TRAP the system. For some system builders this is an acceptable trade-off. +config UBSAN_BOUNDS + bool "Perform array index bounds checking" + depends on UBSAN + 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" + depends on UBSAN + 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 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)