[PATCH 1/5 v11] ARM: Disable KASan instrumentation for some code

Linus Walleij linus.walleij at linaro.org
Tue Jun 30 09:37:32 EDT 2020

From: Andrey Ryabinin <aryabinin at virtuozzo.com>

Disable instrumentation for arch/arm/boot/compressed/*
since that code is executed before the kernel has even
set up its mappings and definately out of scope for

Disable instrumentation of arch/arm/vdso/* because that code
is not linked with the kernel image, so the KASan management
code would fail to link.

Disable instrumentation of arch/arm/mm/physaddr.c. See commit
ec6d06efb0ba ("arm64: Add support for CONFIG_DEBUG_VIRTUAL")
for more details.

Disable kasan check in the function unwind_pop_register because
it does not matter that kasan checks failed when unwind_pop_register()
reads the stack memory of a task.

Cc: Andrey Ryabinin <aryabinin at virtuozzo.com>
Cc: Alexander Potapenko <glider at google.com>
Cc: Dmitry Vyukov <dvyukov at google.com>
Cc: kasan-dev at googlegroups.com
Reviewed-by: Ard Biesheuvel <ardb at kernel.org>
Tested-by: Ard Biesheuvel <ardb at kernel.org> # QEMU/KVM/mach-virt/LPAE/8G
Reported-by: Florian Fainelli <f.fainelli at gmail.com>
Reported-by: Marc Zyngier <marc.zyngier at arm.com>
Signed-off-by: Abbott Liu <liuwenliang at huawei.com>
Signed-off-by: Florian Fainelli <f.fainelli at gmail.com>
Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
ChangeLog v10->v11:
- Resend with the other changes.
ChangeLog v9->v10:
- Rebase on v5.8-rc1
ChangeLog v8->v9:
- Collect Ard's tags.
ChangeLog v7->v8:
- Do not sanitize arch/arm/mm/mmu.c.
  Apart from being intuitively correct, it turns out that KASan
  will insert a __asan_load4() into the set_pte_at() function
  in mmu.c and this is something that KASan calls in the early
  initialization, to set up the shadow memory. Naturally,
  __asan_load4() cannot be called before the shadow memory is
  set up so we need to exclude mmu.c from sanitization.
ChangeLog v6->v7:
- Removed the KVM instrumentaton disablement since KVM
  on ARM32 is gone.
 arch/arm/boot/compressed/Makefile | 1 +
 arch/arm/kernel/unwind.c          | 6 +++++-
 arch/arm/mm/Makefile              | 2 ++
 arch/arm/vdso/Makefile            | 2 ++
 4 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index 00602a6fba04..bb8d193d13de 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -24,6 +24,7 @@ OBJS		+= hyp-stub.o
 # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
index d2bd0df2318d..f35eb584a18a 100644
--- a/arch/arm/kernel/unwind.c
+++ b/arch/arm/kernel/unwind.c
@@ -236,7 +236,11 @@ static int unwind_pop_register(struct unwind_ctrl_block *ctrl,
 		if (*vsp >= (unsigned long *)ctrl->sp_high)
 			return -URC_FAILURE;
-	ctrl->vrs[reg] = *(*vsp)++;
+	/* Use READ_ONCE_NOCHECK here to avoid this memory access
+	 * from being tracked by KASAN.
+	 */
+	ctrl->vrs[reg] = READ_ONCE_NOCHECK(*(*vsp));
+	(*vsp)++;
 	return URC_OK;
diff --git a/arch/arm/mm/Makefile b/arch/arm/mm/Makefile
index 7cb1699fbfc4..99699c32d8a5 100644
--- a/arch/arm/mm/Makefile
+++ b/arch/arm/mm/Makefile
@@ -7,6 +7,7 @@ obj-y				:= extable.o fault.o init.o iomap.o
 obj-y				+= dma-mapping$(MMUEXT).o
 obj-$(CONFIG_MMU)		+= fault-armv.o flush.o idmap.o ioremap.o \
 				   mmap.o pgd.o mmu.o pageattr.o
+KASAN_SANITIZE_mmu.o		:= n
 ifneq ($(CONFIG_MMU),y)
 obj-y				+= nommu.o
@@ -16,6 +17,7 @@ endif
 obj-$(CONFIG_ARM_PTDUMP_CORE)	+= dump.o
 obj-$(CONFIG_ARM_PTDUMP_DEBUGFS)	+= ptdump_debugfs.o
 obj-$(CONFIG_MODULES)		+= proc-syms.o
+KASAN_SANITIZE_physaddr.o	:= n
 obj-$(CONFIG_DEBUG_VIRTUAL)	+= physaddr.o
 obj-$(CONFIG_ALIGNMENT_TRAP)	+= alignment.o
diff --git a/arch/arm/vdso/Makefile b/arch/arm/vdso/Makefile
index d3c9f03e7e79..71d18d59bd35 100644
--- a/arch/arm/vdso/Makefile
+++ b/arch/arm/vdso/Makefile
@@ -42,6 +42,8 @@ GCOV_PROFILE := n
 # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
 # Force dependency
 $(obj)/vdso.o : $(obj)/vdso.so

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