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Message-Id: <20210219230841.875875-1-jiancai@google.com> Date: Fri, 19 Feb 2021 15:08:13 -0800 From: Jian Cai <jiancai@...gle.com> To: unlisted-recipients:; (no To-header on input) Cc: ndesaulniers@...gle.com, manojgupta@...gle.com, llozano@...gle.com, clang-built-linux@...glegroups.com, Jian Cai <jiancai@...gle.com>, Nathan Chancellor <nathan@...nel.org>, David Laight <David.Laight@...lab.com>, Will Deacon <will@...nel.org>, Russell King <linux@...linux.org.uk>, Catalin Marinas <catalin.marinas@....com>, James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>, Arnd Bergmann <arnd@...db.de>, Masahiro Yamada <masahiroy@...nel.org>, Kees Cook <keescook@...omium.org>, Ard Biesheuvel <ardb@...nel.org>, "Andreas Färber" <afaerber@...e.de>, Ingo Molnar <mingo@...nel.org>, Linus Walleij <linus.walleij@...aro.org>, Marc Zyngier <maz@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, Mike Rapoport <rppt@...nel.org>, Mark Rutland <mark.rutland@....com>, David Brazdil <dbrazdil@...gle.com>, James Morse <james.morse@....com>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org Subject: [PATCH v4] ARM: Implement SLS mitigation This patch adds CONFIG_HARDEN_SLS_ALL that can be used to turn on -mharden-sls=all, which mitigates the straight-line speculation vulnerability, speculative execution of the instruction following some unconditional jumps. Notice -mharden-sls= has other options as below, and this config turns on the strongest option. all: enable all mitigations against Straight Line Speculation that are implemented. none: disable all mitigations against Straight Line Speculation. retbr: enable the mitigation against Straight Line Speculation for RET and BR instructions. blr: enable the mitigation against Straight Line Speculation for BLR instructions. Links: https://reviews.llvm.org/D93221 https://reviews.llvm.org/D81404 https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/downloads/straight-line-speculation https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/frequently-asked-questions#SLS2 Suggested-by: Manoj Gupta <manojgupta@...gle.com> Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com> Suggested-by: Nathan Chancellor <nathan@...nel.org> Suggested-by: David Laight <David.Laight@...lab.com> Suggested-by: Will Deacon <will@...nel.org> Reviewed-by: Nathan Chancellor <nathan@...nel.org> Signed-off-by: Jian Cai <jiancai@...gle.com> --- Changes v3 -> v4: Address Nathan's comment and replace def_bool with depends on in HARDEN_SLS_ALL. arch/arm/Makefile | 4 ++++ arch/arm/include/asm/vmlinux.lds.h | 4 ++++ arch/arm/kernel/vmlinux.lds.S | 1 + arch/arm64/Makefile | 4 ++++ arch/arm64/kernel/vmlinux.lds.S | 5 +++++ security/Kconfig.hardening | 10 ++++++++++ 6 files changed, 28 insertions(+) diff --git a/arch/arm/Makefile b/arch/arm/Makefile index 4aaec9599e8a..11d89ef32da9 100644 --- a/arch/arm/Makefile +++ b/arch/arm/Makefile @@ -48,6 +48,10 @@ CHECKFLAGS += -D__ARMEL__ KBUILD_LDFLAGS += -EL endif +ifeq ($(CONFIG_HARDEN_SLS_ALL), y) +KBUILD_CFLAGS += -mharden-sls=all +endif + # # The Scalar Replacement of Aggregates (SRA) optimization pass in GCC 4.9 and # later may result in code being generated that handles signed short and signed diff --git a/arch/arm/include/asm/vmlinux.lds.h b/arch/arm/include/asm/vmlinux.lds.h index 4a91428c324d..c7f9717511ca 100644 --- a/arch/arm/include/asm/vmlinux.lds.h +++ b/arch/arm/include/asm/vmlinux.lds.h @@ -145,3 +145,7 @@ __edtcm_data = .; \ } \ . = __dtcm_start + SIZEOF(.data_dtcm); + +#define SLS_TEXT \ + ALIGN_FUNCTION(); \ + *(.text.__llvm_slsblr_thunk_*) diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S index f7f4620d59c3..e71f2bc97bae 100644 --- a/arch/arm/kernel/vmlinux.lds.S +++ b/arch/arm/kernel/vmlinux.lds.S @@ -63,6 +63,7 @@ SECTIONS .text : { /* Real text segment */ _stext = .; /* Text and read-only data */ ARM_TEXT + SLS_TEXT } #ifdef CONFIG_DEBUG_ALIGN_RODATA diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 90309208bb28..ca7299b356a9 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -34,6 +34,10 @@ $(warning LSE atomics not supported by binutils) endif endif +ifeq ($(CONFIG_HARDEN_SLS_ALL), y) +KBUILD_CFLAGS += -mharden-sls=all +endif + cc_has_k_constraint := $(call try-run,echo \ 'int main(void) { \ asm volatile("and w0, w0, %w0" :: "K" (4294967295)); \ diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 4c0b0c89ad59..f8912e42ffcd 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -93,6 +93,10 @@ jiffies = jiffies_64; #define TRAMP_TEXT #endif +#define SLS_TEXT \ + ALIGN_FUNCTION(); \ + *(.text.__llvm_slsblr_thunk_*) + /* * The size of the PE/COFF section that covers the kernel image, which * runs from _stext to _edata, must be a round multiple of the PE/COFF @@ -144,6 +148,7 @@ SECTIONS HIBERNATE_TEXT TRAMP_TEXT *(.fixup) + SLS_TEXT *(.gnu.warning) . = ALIGN(16); *(.got) /* Global offset table */ diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index 269967c4fc1b..146b75a79d9e 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -121,6 +121,16 @@ choice endchoice +config HARDEN_SLS_ALL + bool "enable SLS vulnerability hardening" + default n + depends on $(cc-option,-mharden-sls=all) + help + Enables straight-line speculation vulnerability hardening on ARM and ARM64 + architectures. It inserts speculation barrier sequences (SB or DSB+ISB + depending on the target architecture) after RET and BR, and replacing + BLR with BL+BR sequence. + config GCC_PLUGIN_STRUCTLEAK_VERBOSE bool "Report forcefully initialized variables" depends on GCC_PLUGIN_STRUCTLEAK -- 2.30.0.617.g56c4b15f3c-goog
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