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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id r8sm10830771pfq.16.2020.06.09.12.09.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Jun 2020 12:09:28 -0700 (PDT) Date: Tue, 9 Jun 2020 12:09:27 -0700 From: Kees Cook To: Will Deacon Cc: Alexander Popov , Emese Revfy , Miguel Ojeda , Masahiro Yamada , Michal Marek , Andrew Morton , Masahiro Yamada , Thiago Jung Bauermann , Luis Chamberlain , Jessica Yu , Sven Schnelle , Iurii Zaikin , Catalin Marinas , Vincenzo Frascino , Thomas Gleixner , Peter Collingbourne , Naohiro Aota , Alexander Monakov , Mathias Krause , PaX Team , Brad Spengler , Laura Abbott , Florian Weimer , kernel-hardening@lists.openwall.com, linux-kbuild@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, gcc@gcc.gnu.org, notify@kernel.org Subject: Re: [PATCH 5/5] gcc-plugins/stackleak: Don't instrument vgettimeofday.c in arm64 VDSO Message-ID: <202006091149.6C78419@keescook> References: <20200604134957.505389-1-alex.popov@linux.com> <20200604134957.505389-6-alex.popov@linux.com> <20200604135806.GA3170@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200604135806.GA3170@willie-the-truck> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 04, 2020 at 02:58:06PM +0100, Will Deacon wrote: > On Thu, Jun 04, 2020 at 04:49:57PM +0300, Alexander Popov wrote: > > Don't try instrumenting functions in arch/arm64/kernel/vdso/vgettimeofday.c. > > Otherwise that can cause issues if the cleanup pass of stackleak gcc plugin > > is disabled. > > > > Signed-off-by: Alexander Popov > > --- > > arch/arm64/kernel/vdso/Makefile | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile > > index 3862cad2410c..9b84cafbd2da 100644 > > --- a/arch/arm64/kernel/vdso/Makefile > > +++ b/arch/arm64/kernel/vdso/Makefile > > @@ -32,7 +32,8 @@ UBSAN_SANITIZE := n > > OBJECT_FILES_NON_STANDARD := y > > KCOV_INSTRUMENT := n > > > > -CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny -fasynchronous-unwind-tables > > +CFLAGS_vgettimeofday.o = -O2 -mcmodel=tiny -fasynchronous-unwind-tables \ > > + $(DISABLE_STACKLEAK_PLUGIN) > > I can pick this one up via arm64, thanks. Are there any other plugins we > should be wary of? It looks like x86 filters out $(GCC_PLUGINS_CFLAGS) > when building the vDSO. I didn't realize/remember that arm64 retained the kernel build flags for vDSO builds. (I'm used to x86 throwing all its flags away for its vDSO.) How does 32-bit ARM do its vDSO? My quick run-through on plugins: arm_ssp_per_task_plugin.c 32-bit ARM only (but likely needs disabling for 32-bit ARM vDSO?) cyc_complexity_plugin.c compile-time reporting only latent_entropy_plugin.c this shouldn't get triggered for the vDSO (no __latent_entropy nor __init attributes in vDSO), but perhaps explicitly disabling it would be a sensible thing to do, just for robustness? randomize_layout_plugin.c this shouldn't get triggered (again, lacking attributes), but should likely be disabled too. sancov_plugin.c This should be tracking the KCOV directly (see scripts/Makefile.kcov), which is already disabled here. structleak_plugin.c This should be fine in the vDSO, but there's not security boundary here, so it wouldn't be important to KEEP it enabled. -- Kees Cook