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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id i187sm9130990pgd.82.2020.09.14.15.13.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2020 15:13:15 -0700 (PDT) Date: Mon, 14 Sep 2020 15:13:14 -0700 From: Kees Cook To: George-Aurelian Popescu Cc: maz@kernel.org, catalin.marinas@arm.com, will@kernel.org, masahiroy@kernel.org, michal.lkml@markovi.net, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, natechancellor@gmail.com, ndesaulniers@google.com, dbrazdil@google.com, broonie@kernel.org, maskray@google.com, ascull@google.com, akpm@linux-foundation.org, dvyukov@google.com, elver@google.com, tglx@linutronix.de, arnd@arndb.de Subject: Re: [PATCH 06/14] Fix CFLAGS for UBSAN_BOUNDS on Clang Message-ID: <202009141509.CDDC8C8@keescook> References: <20200914172750.852684-1-georgepope@google.com> <20200914172750.852684-7-georgepope@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200914172750.852684-7-georgepope@google.com> Sender: linux-kbuild-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org 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 That sounds like a compiler bug? > Signed-off-by: George Popescu > --- > scripts/Makefile.ubsan | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan > index 27348029b2b8..3d15ac346c97 100644 > --- a/scripts/Makefile.ubsan > +++ b/scripts/Makefile.ubsan > @@ -4,7 +4,14 @@ ifdef CONFIG_UBSAN_ALIGNMENT > endif > > ifdef CONFIG_UBSAN_BOUNDS > - CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds) > + # For Clang -fsanitize=bounds translates to -fsanitize=array-bounds and > + # -fsanitize=local-bounds; the latter adds a brk right after the > + # handler is called. > + ifdef CONFIG_CC_IS_CLANG > + CFLAGS_UBSAN += $(call cc-option, -fsanitize=array-bounds) This would mean losing the local-bounds coverage? Isn't that for locally defined arrays on the stack? > + else > + CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds) > + endif > endif > > ifdef CONFIG_UBSAN_MISC > -- > 2.28.0.618.gf4bc123cb7-goog > -- Kees Cook