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Message-ID: <20180720063956.n64a2bgaykzj5xh6@salmiak>
Date: Fri, 20 Jul 2018 07:39:57 +0100
From: Mark Rutland <mark.rutland@....com>
To: Laura Abbott <labbott@...hat.com>
Cc: Alexander Popov <alex.popov@...ux.com>,
Kees Cook <keescook@...omium.org>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
kernel-hardening@...ts.openwall.com,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Will Deacon <will.deacon@....com>,
Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCHv2 2/2] arm64: Clear the stack
On Thu, Jul 19, 2018 at 04:28:06PM -0700, Laura Abbott wrote:
>
> Implementation of stackleak based heavily on the x86 version
>
> Signed-off-by: Laura Abbott <labbott@...hat.com>
Reviewed-by: Mark Rutlamd <mark.rutland@....com>
Thanks for working on this!
Mark.
> ---
> v2: Convert to adjusted on_acessible_stack APIs. Fixed alloca check to
> just panic. Dropped the extra include per Kees. I also didn't add the
> Reviewed-by since the APIs did change and I wanted another pass.
> ---
> arch/arm64/Kconfig | 1 +
> arch/arm64/include/asm/processor.h | 15 +++++++++++++++
> arch/arm64/kernel/entry.S | 7 +++++++
> arch/arm64/kernel/process.c | 17 +++++++++++++++++
> arch/arm64/kvm/hyp/Makefile | 3 ++-
> drivers/firmware/efi/libstub/Makefile | 3 ++-
> 6 files changed, 44 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 42c090cf0292..216d36a49ab5 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -96,6 +96,7 @@ 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 a73ae1e49200..0061450a793b 100644
> --- a/arch/arm64/include/asm/processor.h
> +++ b/arch/arm64/include/asm/processor.h
> @@ -266,5 +266,20 @@ extern void __init minsigstksz_setup(void);
> #define SVE_SET_VL(arg) sve_set_current_vl(arg)
> #define SVE_GET_VL() sve_get_current_vl()
>
> +/*
> + * For CONFIG_GCC_PLUGIN_STACKLEAK
> + *
> + * These need to be macros because otherwise we get stuck in a nightmare
> + * of header definitions for the use of task_stack_page.
> + */
> +
> +#define current_top_of_stack() \
> +({ \
> + struct stack_info _info; \
> + BUG_ON(!on_accessible_stack(current, current_stack_pointer, &_info)); \
> + _info.high; \
> +})
> +#define on_thread_stack() (on_task_stack(current, current_stack_pointer, NULL))
> +
> #endif /* __ASSEMBLY__ */
> #endif /* __ASM_PROCESSOR_H */
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index 28ad8799406f..67d12016063d 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -431,6 +431,11 @@ tsk .req x28 // current thread_info
>
> .text
>
> + .macro stackleak_erase
> +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
> + bl stackleak_erase
> +#endif
> + .endm
> /*
> * Exception vectors.
> */
> @@ -910,6 +915,7 @@ ret_fast_syscall:
> and x2, x1, #_TIF_WORK_MASK
> cbnz x2, work_pending
> enable_step_tsk x1, x2
> + stackleak_erase
> kernel_exit 0
> ret_fast_syscall_trace:
> enable_daif
> @@ -936,6 +942,7 @@ ret_to_user:
> cbnz x2, work_pending
> finish_ret_to_user:
> enable_step_tsk x1, x2
> + stackleak_erase
> kernel_exit 0
> ENDPROC(ret_to_user)
>
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index e10bc363f533..2724e4d31b16 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -493,3 +493,20 @@ void arch_setup_new_exec(void)
> {
> current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0;
> }
> +
> +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
> +void __used stackleak_check_alloca(unsigned long size)
> +{
> + unsigned long stack_left;
> + unsigned long current_sp = current_stack_pointer;
> + struct stack_info info;
> +
> + BUG_ON(!on_accessible_stack(current, current_sp, &info));
> +
> + stack_left = current_sp - info.low;
> +
> + if (size >= stack_left)
> + panic("alloca() over the kernel stack boundary\n");
> +}
> +EXPORT_SYMBOL(stackleak_check_alloca);
> +#endif
> diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile
> index 4313f7475333..2fabc2dc1966 100644
> --- a/arch/arm64/kvm/hyp/Makefile
> +++ b/arch/arm64/kvm/hyp/Makefile
> @@ -3,7 +3,8 @@
> # Makefile for Kernel-based Virtual Machine module, HYP part
> #
>
> -ccflags-y += -fno-stack-protector -DDISABLE_BRANCH_PROFILING
> +ccflags-y += -fno-stack-protector -DDISABLE_BRANCH_PROFILING \
> + $(DISABLE_STACKLEAK_PLUGIN)
>
> KVM=../../../../virt/kvm
>
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index a34e9290a699..25dd2a14560d 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -20,7 +20,8 @@ cflags-$(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
> --
> 2.17.1
>
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