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Message-Id: <20180720214154.2940-3-labbott@redhat.com>
Date: Fri, 20 Jul 2018 14:41:54 -0700
From: Laura Abbott <labbott@...hat.com>
To: Alexander Popov <alex.popov@...ux.com>,
Kees Cook <keescook@...omium.org>,
Mark Rutland <mark.rutland@....com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Laura Abbott <labbott@...hat.com>,
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: [PATCHv3 2/2] arm64: Add support for STACKLEAK gcc plugin
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.
Reviewed-by: Mark Rutland <mark.rutland@....com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Laura Abbott <labbott@...hat.com>
---
v3: Actual commit text courtesy of Kees. A comment explaining why we
panic
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/processor.h | 15 +++++++++++++++
arch/arm64/kernel/entry.S | 7 +++++++
arch/arm64/kernel/process.c | 22 ++++++++++++++++++++++
arch/arm64/kvm/hyp/Makefile | 3 ++-
drivers/firmware/efi/libstub/Makefile | 3 ++-
6 files changed, 49 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..f0ad00fb6a71 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -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
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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