[PATCH v6] ARM: Implement SLS mitigation
From: Jian Cai <hidden>
Date: 2021-03-05 00:53:34
Also in:
linux-arm-kernel, lkml
Subsystem:
arm port, arm64 port (aarch64 architecture), kernel hardening (not covered by other areas), security subsystem, the rest · Maintainers:
Russell King, Catalin Marinas, Will Deacon, Kees Cook, Paul Moore, James Morris, "Serge E. Hallyn", Linus Torvalds
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 <redacted> Suggested-by: Nick Desaulniers <ndesaulniers@google.com> Suggested-by: Nathan Chancellor <nathan@kernel.org> Suggested-by: David Laight <redacted> Suggested-by: Will Deacon <will@kernel.org> Suggested-by: Russell King <redacted> Suggested-by: Linus Walleij <redacted> Signed-off-by: Jian Cai <redacted> --- Changes v1 -> v2: Update the description and patch based on Nathan and David's comments. Changes v2 -> v3: Modify linker scripts as Nick suggested to address boot failure (verified with qemu). Added more details in Kconfig.hardening description. Disable the config by default. Changes v3 -> v4: Address Nathan's comment and replace def_bool with depends on in HARDEN_SLS_ALL. Changes v4 -> v5: Removed "default n" and made the description target indepdent in Kconfig.hardening. Changes v5 -> v6: Add select HARDEN_SLS_ALL under config HARDEN_BRANCH_PREDICTOR. This turns on HARDEN_SLS_ALL by default where applicable. arch/arm/Makefile | 4 ++++ arch/arm/include/asm/vmlinux.lds.h | 4 ++++ arch/arm/kernel/vmlinux.lds.S | 1 + arch/arm/mm/Kconfig | 1 + arch/arm64/Makefile | 4 ++++ arch/arm64/kernel/vmlinux.lds.S | 5 +++++ security/Kconfig.hardening | 8 ++++++++ 7 files changed, 27 insertions(+)
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index dad5502ecc28..54f9b5ff9682 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/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 35f43d0aa056..bdb63e7b1bec 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig@@ -837,6 +837,7 @@ config HARDEN_BRANCH_PREDICTOR bool "Harden the branch predictor against aliasing attacks" if EXPERT depends on CPU_SPECTRE default y + select HARDEN_SLS_ALL help Speculation attacks against some high-performance processors rely on being able to manipulate the branch predictor for a victim
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 5b84aec31ed3..e233bfbdb1c2 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 7eea7888bb02..d5c892605862 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S@@ -103,6 +103,10 @@ 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
@@ -154,6 +158,7 @@ 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..db76ad732c14 100644
--- a/security/Kconfig.hardening
+++ b/security/Kconfig.hardening@@ -121,6 +121,14 @@ choice endchoice +config HARDEN_SLS_ALL + bool "enable SLS vulnerability hardening" + depends on $(cc-option,-mharden-sls=all) + help + Enables straight-line speculation vulnerability hardening. This inserts + speculation barrier instruction sequences after certain unconditional jumps + to prevent speculative execution past those barriers. + config GCC_PLUGIN_STRUCTLEAK_VERBOSE bool "Report forcefully initialized variables" depends on GCC_PLUGIN_STRUCTLEAK
--
2.30.1.766.gb4fecdf3b7-goog