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SubjectRe: [PATCH 00/11] KASan for arm
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On 10/12/2017 12:10 AM, Abbott Liu wrote:
>On 10/11/2017 12:50 PM, Florian Fainelli wrote:
>> 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

>I ended up fixing the redefinition warnings/build failures this way, but
>I am not 100% confident this is the right fix:

>diff --git a/arch/arm/boot/compressed/decompress.c
>b/arch/arm/boot/compressed/decompress.c
>index f3a4bedd1afc..7d4a47752760 100644
>--- a/arch/arm/boot/compressed/decompress.c
>+++ b/arch/arm/boot/compressed/decompress.c
>@@ -48,8 +48,10 @@ extern int memcmp(const void *cs, const void *ct,
>size_t count);
> #endif
>
> #ifdef CONFIG_KERNEL_XZ
>+#ifndef CONFIG_KASAN
> #define memmove memmove
> #define memcpy memcpy
>+#endif
> #include "../../../../lib/decompress_unxz.c"
> #endif
>
>Was not able yet to track down why __memset is not being resolved, but
>since I don't need them, disabled CONFIG_ATAGS and
>CONFIG_ARM_ATAG_DTB_COMPAT and this allowed me to get a build working.
>
>This brought me all the way to a prompt and please find attached the
>results of insmod test_kasan.ko for CONFIG_ARM_LPAE=y and
>CONFIG_ARM_LPAE=n. Your patches actually spotted a genuine use after
>free in one of our drivers (spi-bcm-qspi) so with this:
>
>Tested-by: Florian Fainelli <f.fainelli@gmail.com>
>
>Great job thanks!
>--
>Florian

Thanks for your testing and solution. I'm sorry that I don't test when CONFIG_ATAGS,
CONFIG_ARM_ATAG_DTB_COMPAT and CONFIG_KERNEL_XZ are enabling.

The fellow error:
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'

It can be resolved by the code of Andrey Ryabinin <a.ryabinin@samsung.com> on
https://github.com/aryabinin/linux/commit/0b54f17e70ff50a902c4af05bb92716eb95acefe.
Here is the patch:

--- a/arch/arm/boot/compressed/libfdt_env.h
+++ b/arch/arm/boot/compressed/libfdt_env.h
@@ -16,4 +16,6 @@ typedef __be64 fdt64_t;
#define fdt64_to_cpu(x) be64_to_cpu(x)
#define cpu_to_fdt64(x) cpu_to_be64(x)

+#undef memset
+
#endif

I delete it because I don't know that is needed when CONFIG_ATAGS and
CONFIG_ARM_ATAG_DTB_COMPAT are enabling. I'm sorry for my fault.


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