* [PATCH] kasan: avoid out-of-bounds in unwind_frame
@ 2018-10-09 10:11 Chunhui Li
2018-10-09 10:38 ` Mark Rutland
0 siblings, 1 reply; 3+ messages in thread
From: Chunhui Li @ 2018-10-09 10:11 UTC (permalink / raw)
To: linux-arm-kernel
From: "chunhui.li" <chunhui.li@mediatek.com>
kasan detect unwind_frame out-of-bounds error when one task
dump another, log as below
BUG: KASAN: out-of-bounds in unwind_frame+0x140/0x20c Read of
size 8 at addr ffffffea1e2378e0 by task AnrMonitorThrea/1111
avoid kasan out-of-bounds error by disable kasan for stacktrace.c
Signed-off-by: chunhui.li <chunhui.li@mediatek.com>
---
arch/arm64/kernel/Makefile | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 95ac737..606d0e2 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -57,6 +57,8 @@ arm64-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
arm64-obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o
arm64-obj-$(CONFIG_ARM64_SSBD) += ssbd.o
+KASAN_SANITIZE_stacktrace.o := n
+
obj-y += $(arm64-obj-y) vdso/ probes/
obj-m += $(arm64-obj-m)
head-y := head.o
--
1.9.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [PATCH] kasan: avoid out-of-bounds in unwind_frame
2018-10-09 10:11 [PATCH] kasan: avoid out-of-bounds in unwind_frame Chunhui Li
@ 2018-10-09 10:38 ` Mark Rutland
[not found] ` <193a2b2efdaf41f39cb35a72feb3b39e@MTKMBS32N1.mediatek.inc>
0 siblings, 1 reply; 3+ messages in thread
From: Mark Rutland @ 2018-10-09 10:38 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, Oct 09, 2018 at 06:11:03PM +0800, Chunhui Li wrote:
> From: "chunhui.li" <chunhui.li@mediatek.com>
>
> kasan detect unwind_frame out-of-bounds error when one task
> dump another, log as below
> BUG: KASAN: out-of-bounds in unwind_frame+0x140/0x20c Read of
> size 8 at addr ffffffea1e2378e0 by task AnrMonitorThrea/1111
> avoid kasan out-of-bounds error by disable kasan for stacktrace.c
This doesn't look right. Since unwind_frame uses READ_ONCE_NOCHECK(),
we should never perform an access that KASAN complains about.
I don't think that we should completely disable instrumentation of
stacktrace.c.
Can you please figure out precisely which line KASAN is complaining
about? i.e. use scripts/faddr2line.
Thanks,
Mark.
>
> Signed-off-by: chunhui.li <chunhui.li@mediatek.com>
> ---
> arch/arm64/kernel/Makefile | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> index 95ac737..606d0e2 100644
> --- a/arch/arm64/kernel/Makefile
> +++ b/arch/arm64/kernel/Makefile
> @@ -57,6 +57,8 @@ arm64-obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
> arm64-obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o
> arm64-obj-$(CONFIG_ARM64_SSBD) += ssbd.o
>
> +KASAN_SANITIZE_stacktrace.o := n
> +
> obj-y += $(arm64-obj-y) vdso/ probes/
> obj-m += $(arm64-obj-m)
> head-y := head.o
> --
> 1.9.1
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* 答复: [PATCH] kasan: avoid out-of-bounds in unwind_frame
[not found] ` <193a2b2efdaf41f39cb35a72feb3b39e@MTKMBS32N1.mediatek.inc>
@ 2018-10-10 9:26 ` Mark Rutland
0 siblings, 0 replies; 3+ messages in thread
From: Mark Rutland @ 2018-10-10 9:26 UTC (permalink / raw)
To: linux-arm-kernel
On Wed, Oct 10, 2018 at 06:45:17AM +0000, Chunhui Li (???) wrote:
> Hi Mark,
>
> kasan detect out-of-bounds in stacktrace.c line 70, it's already over READ_ONCE_NOCHECK, but still crash
> kernel-4.9/arch/arm64/kernel/stacktrace.c
> 69frame->sp = fp + 0x10;
> 70frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
>
> we test on Android platform, kernel-4.9 build with clang 6.0.2, we will do experiment to clarify whether compiler related issue.
>
> READ_ONCE_NOCHECK->__read_once_size_nocheck with __no_sanitize_address if enable CONFIG_KASAN
>
> kernel-4.9/include/linux/compiler-gcc.h
> #define __no_sanitize_address __attribute__((no_sanitize_address))
>
> kernel-4.9/include/linux/compiler-clang.h
> #define __no_sanitize_address __attribute__((no_sanitize("address")))
If READ_ONCE_NOCHECK() isn't working as intended, then this is a
compiler issue, and there are bigger problems regardless.
If we need to workaround some compiler issue, that should be done in the
implementation of READ_ONCE_NOCHECK().
Please note that there are other issues with using clang to compile the
kernel; at minimum 7.0.0 is required to build a mainline kernel (and
even then, the LSE atomics have to be explicitly disabled), so if this
only affects 6.0.x, I don't think we need to carry any workaround
upstream.
> there is patch from internet, avoid kasan by wrapping with kasan_disable_current, it seems better.
> https://lore.kernel.org/patchwork/patch/644463
> such as:
> +kasan_disable_current();
> // access fp
> +kasan_enable_current();
Please note that the solution later in the thread [1] was to use
READ_ONCE_NOCHECK().
Thanks,
Mark.
[1] https://lore.kernel.org/patchwork/patch/644463/#829858
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2018-10-09 10:11 [PATCH] kasan: avoid out-of-bounds in unwind_frame Chunhui Li
2018-10-09 10:38 ` Mark Rutland
[not found] ` <193a2b2efdaf41f39cb35a72feb3b39e@MTKMBS32N1.mediatek.inc>
2018-10-10 9:26 ` 答复: " Mark Rutland
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