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[35.205.88.202]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4409d2dfc2fsm62434785e9.33.2025.04.25.10.31.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Apr 2025 10:31:05 -0700 (PDT) Date: Fri, 25 Apr 2025 17:30:57 +0000 From: Mostafa Saleh To: Kees Cook Cc: kvmarm@lists.linux.dev, kasan-dev@googlegroups.com, linux-hardening@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, will@kernel.org, maz@kernel.org, oliver.upton@linux.dev, broonie@kernel.org, catalin.marinas@arm.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, elver@google.com, andreyknvl@gmail.com, ryabinin.a.a@gmail.com, akpm@linux-foundation.org, yuzenghui@huawei.com, suzuki.poulose@arm.com, joey.gouly@arm.com, masahiroy@kernel.org, nathan@kernel.org, nicolas.schier@linux.dev Subject: Re: [PATCH 3/4] KVM: arm64: Introduce CONFIG_UBSAN_KVM_EL2 Message-ID: References: <20250416180440.231949-1-smostafa@google.com> <20250416180440.231949-4-smostafa@google.com> <202504161250.CC5C277A@keescook> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202504161250.CC5C277A@keescook> On Wed, Apr 16, 2025 at 12:54:21PM -0700, Kees Cook wrote: > On Wed, Apr 16, 2025 at 06:04:33PM +0000, Mostafa Saleh wrote: > > Add a new Kconfig CONFIG_UBSAN_KVM_EL2 for KVM which enables > > UBSAN for EL2 code (in protected/nvhe/hvhe) modes. > > This will re-use the same checks enabled for the kernel for > > the hypervisor. The only difference is that for EL2 it always > > emits a "brk" instead of implementing hooks as the hypervisor > > can't print reports. > > > > The KVM code will re-use the same code for the kernel > > "report_ubsan_failure()" so #ifdefs are changed to also have this > > code for CONFIG_UBSAN_KVM_EL2 > > > > Signed-off-by: Mostafa Saleh > > --- > > arch/arm64/kvm/hyp/nvhe/Makefile | 6 ++++++ > > include/linux/ubsan.h | 2 +- > > lib/Kconfig.ubsan | 9 +++++++++ > > lib/ubsan.c | 6 ++++-- > > scripts/Makefile.ubsan | 5 ++++- > > 5 files changed, 24 insertions(+), 4 deletions(-) > > > > diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile > > index b43426a493df..cbe7e12752bc 100644 > > --- a/arch/arm64/kvm/hyp/nvhe/Makefile > > +++ b/arch/arm64/kvm/hyp/nvhe/Makefile > > @@ -99,3 +99,9 @@ KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS), $(KBUILD_CFLAG > > # causes a build failure. Remove profile optimization flags. > > KBUILD_CFLAGS := $(filter-out -fprofile-sample-use=% -fprofile-use=%, $(KBUILD_CFLAGS)) > > KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables > > + > > +ifeq ($(CONFIG_UBSAN_KVM_EL2),y) > > +UBSAN_SANITIZE := y > > +# Always use brk and not hooks > > +ccflags-y += $(CFLAGS_UBSAN_FOR_TRAP) > > +endif > > diff --git a/include/linux/ubsan.h b/include/linux/ubsan.h > > index c843816f5f68..3ab8d38aedb8 100644 > > --- a/include/linux/ubsan.h > > +++ b/include/linux/ubsan.h > > @@ -2,7 +2,7 @@ > > #ifndef _LINUX_UBSAN_H > > #define _LINUX_UBSAN_H > > > > -#ifdef CONFIG_UBSAN_TRAP > > +#if defined(CONFIG_UBSAN_TRAP) || defined(CONFIG_UBSAN_KVM_EL2) > > const char *report_ubsan_failure(u32 check_type); > > #else > > static inline const char *report_ubsan_failure(u32 check_type) > > diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan > > index 4216b3a4ff21..3878858eb473 100644 > > --- a/lib/Kconfig.ubsan > > +++ b/lib/Kconfig.ubsan > > @@ -166,4 +166,13 @@ config TEST_UBSAN > > This is a test module for UBSAN. > > It triggers various undefined behavior, and detect it. > > > > +config UBSAN_KVM_EL2 > > + bool "UBSAN for KVM code at EL2" > > + depends on ARM64 > > + help > > + Enable UBSAN when running on ARM64 with KVM in a split mode > > + (nvhe/hvhe/protected) for the hypervisor code running in EL2. > > + In this mode, any UBSAN violation in EL2 would panic the kernel > > + and information similar to UBSAN_TRAP would be printed. > > + > > endif # if UBSAN > > diff --git a/lib/ubsan.c b/lib/ubsan.c > > index 17993727fc96..a6ca235dd714 100644 > > --- a/lib/ubsan.c > > +++ b/lib/ubsan.c > > @@ -19,7 +19,7 @@ > > > > #include "ubsan.h" > > > > -#ifdef CONFIG_UBSAN_TRAP > > +#if defined(CONFIG_UBSAN_TRAP) || defined(CONFIG_UBSAN_KVM_EL2) > > /* > > * Only include matches for UBSAN checks that are actually compiled in. > > * The mappings of struct SanitizerKind (the -fsanitize=xxx args) to > > @@ -97,7 +97,9 @@ const char *report_ubsan_failure(u32 check_type) > > } > > } > > > > -#else > > +#endif > > + > > +#ifndef CONFIG_UBSAN_TRAP > > static const char * const type_check_kinds[] = { > > "load of", > > "store to", > > diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan > > index 9e35198edbf0..68af6830af0f 100644 > > --- a/scripts/Makefile.ubsan > > +++ b/scripts/Makefile.ubsan > > @@ -1,5 +1,8 @@ > > # SPDX-License-Identifier: GPL-2.0 > > > > +#Shared with KVM/arm64 > > Nitpick: Please add a space between "#" and "Shared", and end the line > with "." I will fix it in v2. > > > +export CFLAGS_UBSAN_FOR_TRAP := $(call cc-option,-fsanitize-trap=undefined,-fsanitize-undefined-trap-on-error) > > + > > # Enable available and selected UBSAN features. > > ubsan-cflags-$(CONFIG_UBSAN_ALIGNMENT) += -fsanitize=alignment > > ubsan-cflags-$(CONFIG_UBSAN_BOUNDS_STRICT) += -fsanitize=bounds-strict > > @@ -10,7 +13,7 @@ ubsan-cflags-$(CONFIG_UBSAN_DIV_ZERO) += -fsanitize=integer-divide-by-zero > > ubsan-cflags-$(CONFIG_UBSAN_UNREACHABLE) += -fsanitize=unreachable > > ubsan-cflags-$(CONFIG_UBSAN_BOOL) += -fsanitize=bool > > ubsan-cflags-$(CONFIG_UBSAN_ENUM) += -fsanitize=enum > > -ubsan-cflags-$(CONFIG_UBSAN_TRAP) += $(call cc-option,-fsanitize-trap=undefined,-fsanitize-undefined-trap-on-error) > > +ubsan-cflags-$(CONFIG_UBSAN_TRAP) += $(CFLAGS_UBSAN_FOR_TRAP) > > Another minor style request: please name this "CFLAGS_UBSAN_TRAP" > (nothing else in Kconfig uses "FOR" like this, and leaving it off sounds > more declarative). I will fix it also in v2. > > > > > export CFLAGS_UBSAN := $(ubsan-cflags-y) > > Otherwise, yes, looks good. > > -- > Kees Cook Thanks, Mostafa