On Tue, 11 Dec 2018 at 11:55, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
>
> On Tue, Dec 11, 2018 at 11:37 AM Anders Roxell <anders.roxell@xxxxxxxxxx> wrote:
> >
> > When option CONFIG_KASAN is enabled toghether with ftrace, function
> > ftrace_graph_caller() gets in to a recursion, via functions
> > kasan_check_read() and kasan_check_write().
> >
> > Breakpoint 2, ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:179
> > 179 mcount_get_pc x0 // function's pc
> > (gdb) bt
> > #0 ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:179
> > #1 0xffffff90101406c8 in ftrace_caller () at ../arch/arm64/kernel/entry-ftrace.S:151
> > #2 0xffffff90106fd084 in kasan_check_write (p=0xffffffc06c170878, size=4) at ../mm/kasan/common.c:105
> > #3 0xffffff90104a2464 in atomic_add_return (v=<optimized out>, i=<optimized out>) at ./include/generated/atomic-instrumented.h:71
> > #4 atomic_inc_return (v=<optimized out>) at ./include/generated/atomic-fallback.h:284
> > #5 trace_graph_entry (trace=0xffffffc03f5ff380) at ../kernel/trace/trace_functions_graph.c:441
> > #6 0xffffff9010481774 in trace_graph_entry_watchdog (trace=<optimized out>) at ../kernel/trace/trace_selftest.c:741
> > #7 0xffffff90104a185c in function_graph_enter (ret=<optimized out>, func=<optimized out>, frame_pointer=18446743799894897728, retp=<optimized out>) at ../kernel/trace/trace_functions_graph.c:196
> > #8 0xffffff9010140628 in prepare_ftrace_return (self_addr=18446743592948977792, parent=0xffffffc03f5ff418, frame_pointer=18446743799894897728) at ../arch/arm64/kernel/ftrace.c:231
> > #9 0xffffff90101406f4 in ftrace_graph_caller () at ../arch/arm64/kernel/entry-ftrace.S:182
> > Backtrace stopped: previous frame identical to this frame (corrupt stack?)
> > (gdb)
> >
> > Rework so that kasan_check_read() and kasan_check_write() is marked with
> > 'notrace'.
> >
> > Signed-off-by: Anders Roxell <anders.roxell@xxxxxxxxxx>
> > ---
> > mm/kasan/common.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> > index 03d5d1374ca7..71507d15712b 100644
> > --- a/mm/kasan/common.c
> > +++ b/mm/kasan/common.c
> > @@ -95,13 +95,13 @@ void kasan_disable_current(void)
> > current->kasan_depth--;
> > }
> >
> > -void kasan_check_read(const volatile void *p, unsigned int size)
> > +void notrace kasan_check_read(const volatile void *p, unsigned int size)
> > {
> > check_memory_region((unsigned long)p, size, false, _RET_IP_);
> > }
> > EXPORT_SYMBOL(kasan_check_read);
> >
> > -void kasan_check_write(const volatile void *p, unsigned int size)
> > +void notrace kasan_check_write(const volatile void *p, unsigned int size)
> > {
> > check_memory_region((unsigned long)p, size, true, _RET_IP_);
> > }
>
> Hi Anders,
>
> Thanks for fixing this!
>
> I wonder if there is some compiler/make flag to turn this off for the
> whole file?
>
> We turn as much instrumentation as possible already for this file in Makefile:
>
> KASAN_SANITIZE := n
> UBSAN_SANITIZE_kasan.o := n
> KCOV_INSTRUMENT := n
> CFLAGS_REMOVE_kasan.o = -pg
> CFLAGS_kasan.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
>
> These functions call check_memory_region, which is presumably inlined.
> But if it's not inlined later in some configuration, or we just
> shuffle code a bit, we can get the same problem again.
Thank you for the review.
I'll send out a v2 shortly where I turned off the hole file.
Cheers,
Anders
