[v1,11/11] perf cs-etm: Smatch: Fix potential NULL pointer dereference

Message ID 20190702103420.27540-12-leo.yan@linaro.org
State New
Headers show
Series
  • perf: Fix errors detected by Smatch
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Commit Message

Leo Yan July 2, 2019, 10:34 a.m.
Based on the following report from Smatch, fix the potential
NULL pointer dereference check.

  tools/perf/util/cs-etm.c:2545
  cs_etm__process_auxtrace_info() error: we previously assumed
  'session->itrace_synth_opts' could be null (see line 2541)

tools/perf/util/cs-etm.c
2541         if (session->itrace_synth_opts && session->itrace_synth_opts->set) {
2542                 etm->synth_opts = *session->itrace_synth_opts;
2543         } else {
2544                 itrace_synth_opts__set_default(&etm->synth_opts,
2545                                 session->itrace_synth_opts->default_no_sample);
                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^
2546                 etm->synth_opts.callchain = false;
2547         }

To dismiss the potential NULL pointer dereference, this patch validates
the pointer 'session->itrace_synth_opts' before access its elements.

Signed-off-by: Leo Yan <leo.yan@linaro.org>

---
 tools/perf/util/cs-etm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

-- 
2.17.1

Comments

Mathieu Poirier July 2, 2019, 5:03 p.m. | #1
Hi Leo,

On Tue, Jul 02, 2019 at 06:34:20PM +0800, Leo Yan wrote:
> Based on the following report from Smatch, fix the potential

> NULL pointer dereference check.

> 

>   tools/perf/util/cs-etm.c:2545

>   cs_etm__process_auxtrace_info() error: we previously assumed

>   'session->itrace_synth_opts' could be null (see line 2541)

> 

> tools/perf/util/cs-etm.c

> 2541         if (session->itrace_synth_opts && session->itrace_synth_opts->set) {

> 2542                 etm->synth_opts = *session->itrace_synth_opts;

> 2543         } else {

> 2544                 itrace_synth_opts__set_default(&etm->synth_opts,

> 2545                                 session->itrace_synth_opts->default_no_sample);

>                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^

> 2546                 etm->synth_opts.callchain = false;

> 2547         }

> 

> To dismiss the potential NULL pointer dereference, this patch validates

> the pointer 'session->itrace_synth_opts' before access its elements.

> 

> Signed-off-by: Leo Yan <leo.yan@linaro.org>

> ---

>  tools/perf/util/cs-etm.c | 2 +-

>  1 file changed, 1 insertion(+), 1 deletion(-)

> 

> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c

> index 0c7776b51045..b79df56eb9df 100644

> --- a/tools/perf/util/cs-etm.c

> +++ b/tools/perf/util/cs-etm.c

> @@ -2540,7 +2540,7 @@ int cs_etm__process_auxtrace_info(union perf_event *event,

>  

>  	if (session->itrace_synth_opts && session->itrace_synth_opts->set) {

>  		etm->synth_opts = *session->itrace_synth_opts;

> -	} else {

> +	} else if (session->itrace_synth_opts) {


This will work but we end up checking session->itrace_synth_opts twice.  I
suggest to check it once and then process with the if/else if valid:

        if (session->itrace_synth_opts) {
                if (session->itrace_synth_opts->set) {
                        ...
                } else {
                        ...
                }
        }

Thanks,
Mathieu

>  		itrace_synth_opts__set_default(&etm->synth_opts,

>  				session->itrace_synth_opts->default_no_sample);

>  		etm->synth_opts.callchain = false;

> -- 

> 2.17.1

>
Leo Yan July 3, 2019, 8:22 a.m. | #2
Hi Mathieu,

On Tue, Jul 02, 2019 at 11:03:06AM -0600, Mathieu Poirier wrote:
> Hi Leo,

> 

> On Tue, Jul 02, 2019 at 06:34:20PM +0800, Leo Yan wrote:

> > Based on the following report from Smatch, fix the potential

> > NULL pointer dereference check.

> > 

> >   tools/perf/util/cs-etm.c:2545

> >   cs_etm__process_auxtrace_info() error: we previously assumed

> >   'session->itrace_synth_opts' could be null (see line 2541)

> > 

> > tools/perf/util/cs-etm.c

> > 2541         if (session->itrace_synth_opts && session->itrace_synth_opts->set) {

> > 2542                 etm->synth_opts = *session->itrace_synth_opts;

> > 2543         } else {

> > 2544                 itrace_synth_opts__set_default(&etm->synth_opts,

> > 2545                                 session->itrace_synth_opts->default_no_sample);

> >                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^

> > 2546                 etm->synth_opts.callchain = false;

> > 2547         }

> > 

> > To dismiss the potential NULL pointer dereference, this patch validates

> > the pointer 'session->itrace_synth_opts' before access its elements.

> > 

> > Signed-off-by: Leo Yan <leo.yan@linaro.org>

> > ---

> >  tools/perf/util/cs-etm.c | 2 +-

> >  1 file changed, 1 insertion(+), 1 deletion(-)

> > 

> > diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c

> > index 0c7776b51045..b79df56eb9df 100644

> > --- a/tools/perf/util/cs-etm.c

> > +++ b/tools/perf/util/cs-etm.c

> > @@ -2540,7 +2540,7 @@ int cs_etm__process_auxtrace_info(union perf_event *event,

> >  

> >  	if (session->itrace_synth_opts && session->itrace_synth_opts->set) {

> >  		etm->synth_opts = *session->itrace_synth_opts;

> > -	} else {

> > +	} else if (session->itrace_synth_opts) {

> 

> This will work but we end up checking session->itrace_synth_opts twice.  I

> suggest to check it once and then process with the if/else if valid:

> 

>         if (session->itrace_synth_opts) {

>                 if (session->itrace_synth_opts->set) {

>                         ...

>                 } else {

>                         ...

>                 }

>         }


Thanks for reviewing.

As discussed with Adrian in another email for intel-pt, it's safe to
remove NULL checking for session->itrace_synth_opts after I reviewed the
code for report/script/inject.  So I'm planning to apply the same change
for cs-etm code.

If you have concern for this, please let me know.

Thanks,
Leo Yan

> >  		itrace_synth_opts__set_default(&etm->synth_opts,

> >  				session->itrace_synth_opts->default_no_sample);

> >  		etm->synth_opts.callchain = false;

> > -- 

> > 2.17.1

> >

Patch

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 0c7776b51045..b79df56eb9df 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -2540,7 +2540,7 @@  int cs_etm__process_auxtrace_info(union perf_event *event,
 
 	if (session->itrace_synth_opts && session->itrace_synth_opts->set) {
 		etm->synth_opts = *session->itrace_synth_opts;
-	} else {
+	} else if (session->itrace_synth_opts) {
 		itrace_synth_opts__set_default(&etm->synth_opts,
 				session->itrace_synth_opts->default_no_sample);
 		etm->synth_opts.callchain = false;