From: Laura Abbott <[email protected]>
This adds support for the STACKLEAK gcc plugin to arm64 by implementing
stackleak_check_alloca(), based heavily on the x86 version, and adding the
two helpers used by the stackleak common code: current_top_of_stack() and
on_thread_stack(). The stack erasure calls are made at syscall returns.
Additionally, this disables the plugin in hypervisor and EFI stub code,
which are out of scope for the protection.
Signed-off-by: Laura Abbott <[email protected]>
[kees: add cast to current_top_of_stack(), tweak commit log & comments]
Signed-off-by: Kees Cook <[email protected]>
---
This is tweaked to be stand-alone from Alexander's series so it can land
via the arm64 tree. (Alexander's v14 pulled one change out already, and
I've lifted the last remaining: the newly needed include in stackleak.h)
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/processor.h | 10 ++++++++++
arch/arm64/kernel/entry.S | 7 +++++++
arch/arm64/kernel/process.c | 16 ++++++++++++++++
arch/arm64/kvm/hyp/Makefile | 3 ++-
drivers/firmware/efi/libstub/Makefile | 3 ++-
6 files changed, 38 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..ca856bda2051 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -266,5 +266,15 @@ 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 the STACKLEAK gcc plugin.
+ *
+ * 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() ((unsigned long)task_stack_page(current) + \
+ THREAD_SIZE)
+#define on_thread_stack() (on_task_stack(current, current_stack_pointer))
+
#endif /* __ASSEMBLY__ */
#endif /* __ASM_PROCESSOR_H */
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 28ad8799406f..80bc93d971f7 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_kstack
+#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..d99281b476b0 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -493,3 +493,19 @@ void arch_setup_new_exec(void)
{
current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0;
}
+
+#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
+#define MIN_STACK_LEFT 256
+
+void __used stackleak_check_alloca(unsigned long size)
+{
+ unsigned long sp, stack_left;
+
+ sp = current_stack_pointer;
+
+ stack_left = sp & (THREAD_SIZE - 1);
+ BUG_ON(stack_left < MIN_STACK_LEFT ||
+ size >= stack_left - MIN_STACK_LEFT);
+}
+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
--
Kees Cook
Pixel Security
On 07/11/2018 05:03 PM, Kees Cook wrote:
> From: Laura Abbott <[email protected]>
>
> This adds support for the STACKLEAK gcc plugin to arm64 by implementing
> stackleak_check_alloca(), based heavily on the x86 version, and adding the
> two helpers used by the stackleak common code: current_top_of_stack() and
> on_thread_stack(). The stack erasure calls are made at syscall returns.
> Additionally, this disables the plugin in hypervisor and EFI stub code,
> which are out of scope for the protection.
>
> Signed-off-by: Laura Abbott <[email protected]>
> [kees: add cast to current_top_of_stack(), tweak commit log & comments]
> Signed-off-by: Kees Cook <[email protected]>
> ---
> This is tweaked to be stand-alone from Alexander's series so it can land
> via the arm64 tree. (Alexander's v14 pulled one change out already, and
> I've lifted the last remaining: the newly needed include in stackleak.h)
> ---
> arch/arm64/Kconfig | 1 +
> arch/arm64/include/asm/processor.h | 10 ++++++++++
> arch/arm64/kernel/entry.S | 7 +++++++
> arch/arm64/kernel/process.c | 16 ++++++++++++++++
> arch/arm64/kvm/hyp/Makefile | 3 ++-
> drivers/firmware/efi/libstub/Makefile | 3 ++-
> 6 files changed, 38 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..ca856bda2051 100644
> --- a/arch/arm64/include/asm/processor.h
> +++ b/arch/arm64/include/asm/processor.h
> @@ -266,5 +266,15 @@ 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 the STACKLEAK gcc plugin.
> + *
> + * 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() ((unsigned long)task_stack_page(current) + \
> + THREAD_SIZE)
> +#define on_thread_stack() (on_task_stack(current, current_stack_pointer))
> +
> #endif /* __ASSEMBLY__ */
> #endif /* __ASM_PROCESSOR_H */
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index 28ad8799406f..80bc93d971f7 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_kstack
> +#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..d99281b476b0 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -493,3 +493,19 @@ void arch_setup_new_exec(void)
> {
> current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0;
> }
> +
> +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
> +#define MIN_STACK_LEFT 256
> +
> +void __used stackleak_check_alloca(unsigned long size)
> +{
> + unsigned long sp, stack_left;
> +
> + sp = current_stack_pointer;
> +
> + stack_left = sp & (THREAD_SIZE - 1);
> + BUG_ON(stack_left < MIN_STACK_LEFT ||
> + size >= stack_left - MIN_STACK_LEFT);
> +}
> +EXPORT_SYMBOL(stackleak_check_alloca);
> +#endif
I think the conclusion was this needs to be re-written to account
for the different stack sizes in the same way as x86.
> 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
>
On Wed, Jul 11, 2018 at 6:45 PM, Laura Abbott <[email protected]> wrote:
>> +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
>> +#define MIN_STACK_LEFT 256
>> +
>> +void __used stackleak_check_alloca(unsigned long size)
>> +{
>> + unsigned long sp, stack_left;
>> +
>> + sp = current_stack_pointer;
>> +
>> + stack_left = sp & (THREAD_SIZE - 1);
>> + BUG_ON(stack_left < MIN_STACK_LEFT ||
>> + size >= stack_left - MIN_STACK_LEFT);
>> +}
>> +EXPORT_SYMBOL(stackleak_check_alloca);
>> +#endif
>
>
> I think the conclusion was this needs to be re-written to account
> for the different stack sizes in the same way as x86.
Oh, whoops! Sorry, I missed that fork of the thread. :)
-Kees
--
Kees Cook
Pixel Security