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

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

Leo Yan July 2, 2019, 10:34 a.m. UTC
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(-)

Comments

Mathieu Poirier July 2, 2019, 5:03 p.m. UTC | #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. UTC | #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 mbox series

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;