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Wed, 02 May 2018 13:33:36 -0700 (PDT) Received: from labbott-redhat.redhat.com ([2601:602:9802:a8dc::d2dd]) by smtp.gmail.com with ESMTPSA id v140-v6sm7141762oie.52.2018.05.02.13.33.33 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 02 May 2018 13:33:35 -0700 (PDT) From: Laura Abbott To: Alexander Popov , Kees Cook , Mark Rutland , Ard Biesheuvel Subject: [PATCH 2/2] arm64: Clear the stack Date: Wed, 2 May 2018 13:33:26 -0700 Message-Id: <20180502203326.9491-3-labbott@redhat.com> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20180502203326.9491-1-labbott@redhat.com> References: <20180502203326.9491-1-labbott@redhat.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20180502_133347_634671_C192C6DF X-CRM114-Status: GOOD ( 21.14 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Laura Abbott , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kernel-hardening@lists.openwall.com MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Implementation of stackleak based heavily on the x86 version Signed-off-by: Laura Abbott --- Now written in C instead of a bunch of assembly. --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/processor.h | 6 ++++ arch/arm64/kernel/Makefile | 3 ++ arch/arm64/kernel/entry.S | 6 ++++ arch/arm64/kernel/erase.c | 55 +++++++++++++++++++++++++++++++++++ arch/arm64/kernel/process.c | 16 ++++++++++ drivers/firmware/efi/libstub/Makefile | 3 +- scripts/Makefile.gcc-plugins | 5 +++- 8 files changed, 93 insertions(+), 2 deletions(-) create mode 100644 arch/arm64/kernel/erase.c diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index eb2cf4938f6d..b0221db95dc9 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -92,6 +92,7 @@ config ARM64 select HAVE_ARCH_MMAP_RND_BITS select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT select HAVE_ARCH_SECCOMP_FILTER + select HAVE_ARCH_STACKLEAK select HAVE_ARCH_THREAD_STRUCT_WHITELIST select HAVE_ARCH_TRACEHOOK select HAVE_ARCH_TRANSPARENT_HUGEPAGE diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 767598932549..d31ab80ff647 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -124,6 +124,12 @@ struct thread_struct { unsigned long fault_address; /* fault info */ unsigned long fault_code; /* ESR_EL1 value */ struct debug_info debug; /* debugging */ +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK + unsigned long lowest_stack; +#ifdef CONFIG_STACKLEAK_METRICS + unsigned long prev_lowest_stack; +#endif +#endif }; static inline void arch_thread_struct_whitelist(unsigned long *offset, diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index bf825f38d206..0ceea613c65b 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -55,6 +55,9 @@ arm64-reloc-test-y := reloc_test_core.o reloc_test_syms.o arm64-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o arm64-obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o +arm64-obj-$(CONFIG_GCC_PLUGIN_STACKLEAK) += erase.o +KASAN_SANITIZE_erase.o := n + obj-y += $(arm64-obj-y) vdso/ probes/ obj-m += $(arm64-obj-m) head-y := head.o diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index ec2ee720e33e..3144f1ebdc18 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -401,6 +401,11 @@ tsk .req x28 // current thread_info .text + .macro ERASE_KSTACK +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK + bl erase_kstack +#endif + .endm /* * Exception vectors. */ @@ -906,6 +911,7 @@ ret_to_user: cbnz x2, work_pending finish_ret_to_user: enable_step_tsk x1, x2 + ERASE_KSTACK kernel_exit 0 ENDPROC(ret_to_user) diff --git a/arch/arm64/kernel/erase.c b/arch/arm64/kernel/erase.c new file mode 100644 index 000000000000..b8b5648d893b --- /dev/null +++ b/arch/arm64/kernel/erase.c @@ -0,0 +1,55 @@ +#include +#include +#include +#include +#include + +asmlinkage void erase_kstack(void) +{ + unsigned long p = current->thread.lowest_stack; + unsigned long boundary = p & ~(THREAD_SIZE - 1); + unsigned long poison = 0; + const unsigned long check_depth = STACKLEAK_POISON_CHECK_DEPTH / + sizeof(unsigned long); + + /* + * Let's search for the poison value in the stack. + * Start from the lowest_stack and go to the bottom. + */ + while (p > boundary && poison <= check_depth) { + if (*(unsigned long *)p == STACKLEAK_POISON) + poison++; + else + poison = 0; + + p -= sizeof(unsigned long); + } + + /* + * One long int at the bottom of the thread stack is reserved and + * should not be poisoned (see CONFIG_SCHED_STACK_END_CHECK). + */ + if (p == boundary) + p += sizeof(unsigned long); + +#ifdef CONFIG_STACKLEAK_METRICS + current->thread.prev_lowest_stack = p; +#endif + + /* + * So let's write the poison value to the kernel stack. + * Start from the address in p and move up till the new boundary. + */ + boundary = current_stack_pointer; + + BUG_ON(boundary - p >= THREAD_SIZE); + + while (p < boundary) { + *(unsigned long *)p = STACKLEAK_POISON; + p += sizeof(unsigned long); + } + + /* Reset the lowest_stack value for the next syscall */ + current->thread.lowest_stack = current_stack_pointer; +} + diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index f08a2ed9db0d..156fa0a0da19 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -364,6 +364,9 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start, p->thread.cpu_context.pc = (unsigned long)ret_from_fork; p->thread.cpu_context.sp = (unsigned long)childregs; +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK + p->thread.lowest_stack = (unsigned long)task_stack_page(p); +#endif ptrace_hw_copy_thread(p); return 0; @@ -493,3 +496,16 @@ void arch_setup_new_exec(void) { current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0; } + +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK +void __used check_alloca(unsigned long size) +{ + unsigned long sp, stack_left; + + sp = current_stack_pointer; + + stack_left = sp & (THREAD_SIZE - 1); + BUG_ON(stack_left < 256 || size >= stack_left - 256); +} +EXPORT_SYMBOL(check_alloca); +#endif diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index a34e9290a699..25dd2a14560d 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -20,7 +20,8 @@ cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \ -D__NO_FORTIFY \ $(call cc-option,-ffreestanding) \ - $(call cc-option,-fno-stack-protector) + $(call cc-option,-fno-stack-protector) \ + $(DISABLE_STACKLEAK_PLUGIN) GCOV_PROFILE := n KASAN_SANITIZE := n diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins index 8d6070fc538f..6cc0e35d3324 100644 --- a/scripts/Makefile.gcc-plugins +++ b/scripts/Makefile.gcc-plugins @@ -37,11 +37,14 @@ ifdef CONFIG_GCC_PLUGINS gcc-plugin-$(CONFIG_GCC_PLUGIN_STACKLEAK) += stackleak_plugin.so gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK) += -DSTACKLEAK_PLUGIN -fplugin-arg-stackleak_plugin-track-min-size=$(CONFIG_STACKLEAK_TRACK_MIN_SIZE) + ifdef CONFIG_GCC_PLUGIN_STACKLEAK + DISABLE_STACKLEAK_PLUGIN += -fplugin-arg-stackleak_plugin-disable + endif GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y)) export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGIN GCC_PLUGIN_SUBDIR - export SANCOV_PLUGIN DISABLE_LATENT_ENTROPY_PLUGIN + export SANCOV_PLUGIN DISABLE_LATENT_ENTROPY_PLUGIN DISABLE_STACKLEAK_PLUGIN ifneq ($(PLUGINCC),) # SANCOV_PLUGIN can be only in CFLAGS_KCOV because avoid duplication.