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arm64: Add support for STACKLEAK gcc plugin

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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.

Acked-by: Alexander Popov <alex.popov@linux.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Laura Abbott 2018-07-20 14:41:54 -07:00 committed by Will Deacon
parent 8a1ccfbc9e
commit 0b3e336601
6 changed files with 45 additions and 2 deletions
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1
arch/arm64/Kconfig
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@ -108,6 +108,7 @@ 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

15
arch/arm64/include/asm/processor.h
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@ -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 */

3
arch/arm64/kernel/entry.S
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@ -902,6 +902,9 @@ ret_to_user:
cbnz x2, work_pending
finish_ret_to_user:
enable_step_tsk x1, x2
#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
bl stackleak_erase
#endif
kernel_exit 0
ENDPROC(ret_to_user)

22
arch/arm64/kernel/process.c
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@ -493,3 +493,25 @@ 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;
/*
* There's a good chance we're almost out of stack space if this
* is true. Using panic() over BUG() is more likely to give
* reliable debugging output.
*/
if (size >= stack_left)
panic("alloca() over the kernel stack boundary\n");
}
EXPORT_SYMBOL(stackleak_check_alloca);
#endif

3
arch/arm64/kvm/hyp/Makefile
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@ -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

3
drivers/firmware/efi/libstub/Makefile
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@ -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