Re: [PATCH 00/11] KASan for arm

From: Florian Fainelli
Date: Wed Oct 11 2017 - 15:50:33 EST

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On 10/11/2017 12:13 PM, Florian Fainelli wrote:
> Hi Abbott,
>
> On 10/11/2017 01:22 AM, Abbott Liu wrote:
>> Hi,all:
>> These patches add arch specific code for kernel address sanitizer
>> (see Documentation/kasan.txt).
>>
>> 1/8 of kernel addresses reserved for shadow memory. There was no
>> big enough hole for this, so virtual addresses for shadow were
>> stolen from user space.
>>
>> At early boot stage the whole shadow region populated with just
>> one physical page (kasan_zero_page). Later, this page reused
>> as readonly zero shadow for some memory that KASan currently
>> don't track (vmalloc).
>>
>> After mapping the physical memory, pages for shadow memory are
>> allocated and mapped.
>>
>> KASan's stack instrumentation significantly increases stack's
>> consumption, so CONFIG_KASAN doubles THREAD_SIZE.
>>
>> Functions like memset/memmove/memcpy do a lot of memory accesses.
>> If bad pointer passed to one of these function it is important
>> to catch this. Compiler's instrumentation cannot do this since
>> these functions are written in assembly.
>>
>> KASan replaces memory functions with manually instrumented variants.
>> Original functions declared as weak symbols so strong definitions
>> in mm/kasan/kasan.c could replace them. Original functions have aliases
>> with '__' prefix in name, so we could call non-instrumented variant
>> if needed.
>>
>> Some files built without kasan instrumentation (e.g. mm/slub.c).
>> Original mem* function replaced (via #define) with prefixed variants
>> to disable memory access checks for such files.
>>
>> On arm LPAE architecture, the mapping table of KASan shadow memory(if
>> PAGE_OFFSET is 0xc0000000, the KASan shadow memory's virtual space is
>> 0xb6e000000~0xbf000000) can't be filled in do_translation_fault function,
>> because kasan instrumentation maybe cause do_translation_fault function
>> accessing KASan shadow memory. The accessing of KASan shadow memory in
>> do_translation_fault function maybe cause dead circle. So the mapping table
>> of KASan shadow memory need be copyed in pgd_alloc function.
>>
>>
>> Most of the code comes from:
>> https://github.com/aryabinin/linux/commit/0b54f17e70ff50a902c4af05bb92716eb95acefe.
>
> Thanks for putting these patches together, I can't get a kernel to build
> with ARM_LPAE=y or ARM_LPAE=n that does not result in the following:
>
> AS arch/arm/kernel/entry-common.o
> arch/arm/kernel/entry-common.S: Assembler messages:
> arch/arm/kernel/entry-common.S:53: Error: invalid constant
> (ffffffffb6e00000) after fixup
> arch/arm/kernel/entry-common.S:118: Error: invalid constant
> (ffffffffb6e00000) after fixup
> scripts/Makefile.build:412: recipe for target
> 'arch/arm/kernel/entry-common.o' failed
> make[3]: *** [arch/arm/kernel/entry-common.o] Error 1
> Makefile:1019: recipe for target 'arch/arm/kernel' failed
> make[2]: *** [arch/arm/kernel] Error 2
> make[2]: *** Waiting for unfinished jobs....
>
> This is coming from the increase in TASK_SIZE it seems.
>
> This is on top of v4.14-rc4-84-gff5abbe799e2

Seems like we can use the following to get through that build failure:

diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 99c908226065..0de1160d136e 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -50,7 +50,13 @@ ret_fast_syscall:
UNWIND(.cantunwind )
disable_irq_notrace @ disable interrupts
ldr r2, [tsk, #TI_ADDR_LIMIT]
+#ifdef CONFIG_KASAN
+ movw r1, #:lower16:TASK_SIZE
+ movt r1, #:upper16:TASK_SIZE
+ cmp r2, r1
+#else
cmp r2, #TASK_SIZE
+#endif
blne addr_limit_check_failed
ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall
tracing
tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
@@ -115,7 +121,13 @@ ret_slow_syscall:
disable_irq_notrace @ disable interrupts
ENTRY(ret_to_user_from_irq)
ldr r2, [tsk, #TI_ADDR_LIMIT]
+#ifdef CONFIG_KASAN
+ movw r1, #:lower16:TASK_SIZE
+ movt r1, #:upper16:TASK_SIZE
+ cmp r2, r1
+#else
cmp r2, #TASK_SIZE
+#endif
blne addr_limit_check_failed
ldr r1, [tsk, #TI_FLAGS]
tst r1, #_TIF_WORK_MASK

but then we will see another set of build failures with the decompressor
code:

WARNING: modpost: Found 2 section mismatch(es).
To see full details build your kernel with:
'make CONFIG_DEBUG_SECTION_MISMATCH=y'
KSYM .tmp_kallsyms1.o
KSYM .tmp_kallsyms2.o
LD vmlinux
SORTEX vmlinux
SYSMAP System.map
OBJCOPY arch/arm/boot/Image
Kernel: arch/arm/boot/Image is ready
LDS arch/arm/boot/compressed/vmlinux.lds
AS arch/arm/boot/compressed/head.o
XZKERN arch/arm/boot/compressed/piggy_data
CC arch/arm/boot/compressed/misc.o
CC arch/arm/boot/compressed/decompress.o
CC arch/arm/boot/compressed/string.o
arch/arm/boot/compressed/decompress.c:51:0: warning: "memmove" redefined
#define memmove memmove

In file included from arch/arm/boot/compressed/decompress.c:7:0:
./arch/arm/include/asm/string.h:67:0: note: this is the location of the
previous definition
#define memmove(dst, src, len) __memmove(dst, src, len)

arch/arm/boot/compressed/decompress.c:52:0: warning: "memcpy" redefined
#define memcpy memcpy

In file included from arch/arm/boot/compressed/decompress.c:7:0:
./arch/arm/include/asm/string.h:66:0: note: this is the location of the
previous definition
#define memcpy(dst, src, len) __memcpy(dst, src, len)

SHIPPED arch/arm/boot/compressed/hyp-stub.S
SHIPPED arch/arm/boot/compressed/fdt_rw.c
SHIPPED arch/arm/boot/compressed/fdt.h
SHIPPED arch/arm/boot/compressed/libfdt.h
SHIPPED arch/arm/boot/compressed/libfdt_internal.h
SHIPPED arch/arm/boot/compressed/fdt_ro.c
SHIPPED arch/arm/boot/compressed/fdt_wip.c
SHIPPED arch/arm/boot/compressed/fdt.c
CC arch/arm/boot/compressed/atags_to_fdt.o
SHIPPED arch/arm/boot/compressed/lib1funcs.S
SHIPPED arch/arm/boot/compressed/ashldi3.S
SHIPPED arch/arm/boot/compressed/bswapsdi2.S
AS arch/arm/boot/compressed/hyp-stub.o
CC arch/arm/boot/compressed/fdt_rw.o
CC arch/arm/boot/compressed/fdt_ro.o
CC arch/arm/boot/compressed/fdt_wip.o
CC arch/arm/boot/compressed/fdt.o
AS arch/arm/boot/compressed/lib1funcs.o
AS arch/arm/boot/compressed/ashldi3.o
AS arch/arm/boot/compressed/bswapsdi2.o
AS arch/arm/boot/compressed/piggy.o
LD arch/arm/boot/compressed/vmlinux
arch/arm/boot/compressed/decompress.o: In function `fill_temp':
/home/fainelli/dev/linux/arch/arm/boot/compressed/../../../../lib/xz/xz_dec_stream.c:162:
undefined reference to `memcpy'
arch/arm/boot/compressed/decompress.o: In function `bcj_flush':
/home/fainelli/dev/linux/arch/arm/boot/compressed/../../../../lib/xz/xz_dec_bcj.c:404:
undefined reference to `memcpy'
/home/fainelli/dev/linux/arch/arm/boot/compressed/../../../../lib/xz/xz_dec_bcj.c:409:
undefined reference to `memmove'
arch/arm/boot/compressed/decompress.o: In function `lzma2_lzma':
/home/fainelli/dev/linux/arch/arm/boot/compressed/../../../../lib/xz/xz_dec_lzma2.c:919:
undefined reference to `memcpy'
arch/arm/boot/compressed/decompress.o: In function `dict_flush':
/home/fainelli/dev/linux/arch/arm/boot/compressed/../../../../lib/xz/xz_dec_lzma2.c:424:
undefined reference to `memcpy'
arch/arm/boot/compressed/decompress.o: In function `dict_uncompressed':
/home/fainelli/dev/linux/arch/arm/boot/compressed/../../../../lib/xz/xz_dec_lzma2.c:390:
undefined reference to `memcpy'
/home/fainelli/dev/linux/arch/arm/boot/compressed/../../../../lib/xz/xz_dec_lzma2.c:400:
undefined reference to `memcpy'
arch/arm/boot/compressed/decompress.o: In function `lzma2_lzma':
/home/fainelli/dev/linux/arch/arm/boot/compressed/../../../../lib/xz/xz_dec_lzma2.c:859:
undefined reference to `memcpy'
/home/fainelli/dev/linux/arch/arm/boot/compressed/../../../../lib/xz/xz_dec_lzma2.c:884:
undefined reference to `memmove'
arch/arm/boot/compressed/decompress.o: In function `xz_dec_bcj_run':
/home/fainelli/dev/linux/arch/arm/boot/compressed/../../../../lib/xz/xz_dec_bcj.c:451:
undefined reference to `memcpy'
/home/fainelli/dev/linux/arch/arm/boot/compressed/../../../../lib/xz/xz_dec_bcj.c:471:
undefined reference to `memcpy'
arch/arm/boot/compressed/fdt_rw.o: In function `fdt_add_subnode_namelen':
/home/fainelli/dev/linux/arch/arm/boot/compressed/fdt_rw.c:366:
undefined reference to `__memset'
arch/arm/boot/compressed/Makefile:182: recipe for target
'arch/arm/boot/compressed/vmlinux' failed
make[4]: *** [arch/arm/boot/compressed/vmlinux] Error 1
arch/arm/boot/Makefile:53: recipe for target
'arch/arm/boot/compressed/vmlinux' failed
make[3]: *** [arch/arm/boot/compressed/vmlinux] Error 2

>
> Thank you
>
>>
>> These patches are tested on vexpress-ca15, vexpress-ca9
>>
>> Cc: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx>
>> Tested-by: Abbott Liu <liuwenliang@xxxxxxxxxx>
>> Signed-off-by: Abbott Liu <liuwenliang@xxxxxxxxxx>
>>
>> Abbott Liu (6):
>> Define the virtual space of KASan's shadow region
>> change memory_is_poisoned_16 for aligned error
>> Add support arm LPAE
>> Don't need to map the shadow of KASan's shadow memory
>> Change mapping of kasan_zero_page int readonly
>> Add KASan layout
>>
>> Andrey Ryabinin (5):
>> Initialize the mapping of KASan shadow memory
>> replace memory function
>> arm: Kconfig: enable KASan
>> Disable kasan's instrumentation
>> Avoid cleaning the KASan shadow area's mapping table
>>
>> arch/arm/Kconfig | 1 +
>> arch/arm/boot/compressed/Makefile | 1 +
>> arch/arm/include/asm/kasan.h | 20 +++
>> arch/arm/include/asm/kasan_def.h | 51 +++++++
>> arch/arm/include/asm/memory.h | 5 +
>> arch/arm/include/asm/pgalloc.h | 5 +-
>> arch/arm/include/asm/pgtable.h | 1 +
>> arch/arm/include/asm/proc-fns.h | 33 +++++
>> arch/arm/include/asm/string.h | 18 ++-
>> arch/arm/include/asm/thread_info.h | 4 +
>> arch/arm/kernel/entry-armv.S | 7 +-
>> arch/arm/kernel/head-common.S | 4 +
>> arch/arm/kernel/setup.c | 2 +
>> arch/arm/kernel/unwind.c | 3 +-
>> arch/arm/lib/memcpy.S | 3 +
>> arch/arm/lib/memmove.S | 5 +-
>> arch/arm/lib/memset.S | 3 +
>> arch/arm/mm/Makefile | 5 +
>> arch/arm/mm/init.c | 6 +
>> arch/arm/mm/kasan_init.c | 265 +++++++++++++++++++++++++++++++++++++
>> arch/arm/mm/mmu.c | 7 +-
>> arch/arm/mm/pgd.c | 12 ++
>> arch/arm/vdso/Makefile | 2 +
>> mm/kasan/kasan.c | 22 ++-
>> 24 files changed, 478 insertions(+), 7 deletions(-)
>> create mode 100644 arch/arm/include/asm/kasan.h
>> create mode 100644 arch/arm/include/asm/kasan_def.h
>> create mode 100644 arch/arm/mm/kasan_init.c
>>
>
>

--
Florian

Next message: kernel test robot: "[locking/paravirt] 9043442b43: WARNING:at_kernel/jump_label.c:#static_key_disable_cpuslocked"
Previous message: Brijesh Singh: "Re: [Part2 PATCH v5.1 12.4/31] crypto: ccp: Implement SEV_PLATFORM_STATUS ioctl command"
In reply to: Florian Fainelli: "Re: [PATCH 00/11] KASan for arm"
Next in thread: Florian Fainelli: "Re: [PATCH 00/11] KASan for arm"
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