Messages in this thread | | | Date | Wed, 10 Oct 2018 10:26:18 +0100 | From | Mark Rutland <> | Subject | Re: 答复 : [PATCH] kasan: avoid out-of-bounds in unwind_frame |
| |
On Wed, Oct 10, 2018 at 06:45:17AM +0000, Chunhui Li (李春辉) 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
| |