From patchwork Wed Nov 20 01:06:35 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 11252945 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 0DF8E1593 for ; Wed, 20 Nov 2019 01:07:05 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 60EAB2245C for ; Wed, 20 Nov 2019 01:07:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="Dl72hrPu" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 60EAB2245C 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-17404-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 25791 invoked by uid 550); 20 Nov 2019 01:06:56 -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 24562 invoked from network); 20 Nov 2019 01:06:54 -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=Qk+ofBX2bx2BOGB4TqoJ+/VT2N5xkCBYGbqC21Di0lw=; b=Dl72hrPuwamrfPqyV6plvaUBtf5zRowEghIpoZqmgJgFOczuF7EKzjTanI6iefsS9Z 9TvygmIVih8TjwrgaGRcecyP/tDTc7gHkW1za6Qsa+kQOjj0UpGf+owodcIUwPQ/ZSDu QgLC6/NCcIR5lG7LQGAW6FZc2y8odHX4FtywQ= 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=Qk+ofBX2bx2BOGB4TqoJ+/VT2N5xkCBYGbqC21Di0lw=; b=N4XlaO1KwOUk5LzqSY2QnX0XFOFkZdjCs9OT+TXgLu2cPAHJHe45Y3Rt4/Z9f5pu0W 59tOqw07/BbRmKp0OPAjzKM/AjG7p27POMtlhfKSHz4EffwIN4mt2JbIpOS3N/2+enAD aIzZyviV5dGa2wxYjF25CIv1WpAVXrYIXJUT8jxEDgJUBxx7FT6o8Qd1G2lVNz6ktKJt KfVskm467nF4juXF3aacZ1ToAcwh3Plku+AbM5S7knoEDld9xwMFyRAJC0xQAum6Phpu MhSYTTpTJeHQmI+5LsLhrS5LbMMhqDkFCkV4iRpWfU46MwJ3uy6+98DvuC4e6lwxDC8T Uq/g== X-Gm-Message-State: APjAAAWLRGSv+PZBPVXtt109hif+PUO7CPQrm5GKCUEwNfwUyd5LiJmw 80MJyAyhJ/LQzlh5eKpjlhlQdA== X-Google-Smtp-Source: APXvYqwU4vILON4RTm6tdSJVl700JzP/ajHyi1fFkaWh7maGAK9WWWqyZPY7AO1vwzjH8oRIUlhNnw== X-Received: by 2002:a63:5d10:: with SMTP id r16mr80693pgb.41.1574212003024; Tue, 19 Nov 2019 17:06:43 -0800 (PST) From: Kees Cook To: Andrey Ryabinin Cc: Kees Cook , Elena Petrova , Alexander Potapenko , Dmitry Vyukov , Linus Torvalds , Dan Carpenter , "Gustavo A. R. Silva" , Arnd Bergmann , Ard Biesheuvel , Andrew Morton , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: [PATCH 2/3] ubsan: Split "bounds" checker from other options Date: Tue, 19 Nov 2019 17:06:35 -0800 Message-Id: <20191120010636.27368-3-keescook@chromium.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191120010636.27368-1-keescook@chromium.org> References: <20191120010636.27368-1-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 | 19 +++++++++++++++++++ scripts/Makefile.ubsan | 7 ++++++- 2 files changed, 25 insertions(+), 1 deletion(-) diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan index d69e8b21ebae..f5ed2dceef30 100644 --- a/lib/Kconfig.ubsan +++ b/lib/Kconfig.ubsan @@ -22,6 +22,25 @@ config UBSAN_TRAP can just issue a trap. This reduces the kernel size overhead but turns all warnings into full thread-killing exceptions. +config UBSAN_BOUNDS + bool "Perform array bounds checking" + depends on UBSAN + default UBSAN + help + This option enables detection of direct out of bounds array + accesses, where the array size is known at compile time. Note + that this does not protect character array overflows due to + bad calls to the {str,mem}*cpy() family of functions. + +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)