kasan: mark kasan_check_(read|write) as 'notrace'

Message ID 20181211103733.22284-1-anders.roxell@linaro.org
State New
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  • kasan: mark kasan_check_(read|write) as 'notrace'
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Commit Message

Anders Roxell Dec. 11, 2018, 10:37 a.m.
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@linaro.org>

---
 mm/kasan/common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

-- 
2.19.2

Comments

Dmitry Vyukov Dec. 11, 2018, 10:55 a.m. | #1
On Tue, Dec 11, 2018 at 11:37 AM Anders Roxell <anders.roxell@linaro.org> 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@linaro.org>

> ---

>  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.
Anders Roxell Dec. 12, 2018, 6:35 p.m. | #2
On Tue, 11 Dec 2018 at 11:55, Dmitry Vyukov <dvyukov@google.com> wrote:
>

> On Tue, Dec 11, 2018 at 11:37 AM Anders Roxell <anders.roxell@linaro.org> 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@linaro.org>

> > ---

> >  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

Patch

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_);
 }