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[34.77.222.49]) by smtp.gmail.com with ESMTPSA id u66sm3770553wme.12.2020.09.16.00.40.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Sep 2020 00:40:29 -0700 (PDT) Date: Wed, 16 Sep 2020 07:40:27 +0000 From: George Popescu To: Marco Elver Cc: Kees Cook , maz@kernel.org, Catalin Marinas , Will Deacon , Masahiro Yamada , Michal Marek , Linux ARM , kvmarm@lists.cs.columbia.edu, LKML , Linux Kbuild mailing list , clang-built-linux , james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, Nathan Chancellor , Nick Desaulniers , David Brazdil , broonie@kernel.org, Fangrui Song , Andrew Scull , Andrew Morton , Dmitry Vyukov , Thomas Gleixner , Arnd Bergmann Subject: Re: [PATCH 06/14] Fix CFLAGS for UBSAN_BOUNDS on Clang Message-ID: <20200916074027.GA2946587@google.com> References: <20200914172750.852684-1-georgepope@google.com> <20200914172750.852684-7-georgepope@google.com> <202009141509.CDDC8C8@keescook> <20200915102458.GA1650630@google.com> <20200915120105.GA2294884@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 15, 2020 at 07:32:28PM +0200, Marco Elver wrote: > On Tue, 15 Sep 2020 at 14:01, George Popescu wrote: > > > > On Tue, Sep 15, 2020 at 01:18:11PM +0200, Marco Elver wrote: > > > On Tue, 15 Sep 2020 at 12:25, George Popescu wrote: > > > > On Mon, Sep 14, 2020 at 03:13:14PM -0700, Kees Cook wrote: > > > > > On Mon, Sep 14, 2020 at 05:27:42PM +0000, George-Aurelian Popescu wrote: > > > > > > From: George Popescu > > > > > > > > > > > > When the kernel is compiled with Clang, UBSAN_BOUNDS inserts a brk after > > > > > > the handler call, preventing it from printing any information processed > > > > > > inside the buffer. > > > > > > For Clang -fsanitize=bounds expands to -fsanitize=array-bounds and > > > > > > -fsanitize=local-bounds, and the latter adds a brk after the handler > > > > > > call > > > > > > > > > This would mean losing the local-bounds coverage. I tried to test it without > > > > local-bounds and with a locally defined array on the stack and it works fine > > > > (the handler is called and the error reported). For me it feels like > > > > --array-bounds and --local-bounds are triggered for the same type of > > > > undefined_behaviours but they are handling them different. > > > > > > Does -fno-sanitize-trap=bounds help?> > > > > I tried replacing it with: > > ifdef CONFIG_CC_IS_CLANG > > CFLAGS_UBSAN += $(call cc-option, -fno-sanitize-trap=bounds) > > CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds) > > else > > CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds) > > endif > > > > The code traps. > > What's your config? Do you have CONFIG_UBSAN_TRAP=y? If so, you have 2 > options: honor UBSAN_TRAP and crash the kernel, or have a > 'CFLAGS_REMOVE_... = -fsanitize-undefined-trap-on-error' for the files > where you can't deal with traps> I don't have CONFIG_UBSAN_TRAP=y. My .config is: CONFIG_ARCH_HAS_UBSAN_SANITIZE_ALL=y CONFIG_UBSAN=y # CONFIG_UBSAN_TRAP is not set CONFIG_UBSAN_KCOV_BROKEN=y CONFIG_UBSAN_MISC=y CONFIG_UBSAN_SANITIZE_ALL=y # CONFIG_UBSAN_ALIGNMENT is not set CONFIG_TEST_UBSAN=m Thanks, George