| Message ID | 20190702103420.27540-11-leo.yan@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | perf: Fix errors detected by Smatch | expand |
On 2/07/19 1:34 PM, Leo Yan wrote: > Based on the following report from Smatch, fix the potential > NULL pointer dereference check. It never is NULL. Remove the NULL test if you want: - if (session->itrace_synth_opts && session->itrace_synth_opts->set) { + if (session->itrace_synth_opts->set) { But blindly making changes like below is questionable. > > tools/perf/util/intel-pt.c:3200 > intel_pt_process_auxtrace_info() error: we previously assumed > 'session->itrace_synth_opts' could be null (see line 3196) > > tools/perf/util/intel-pt.c:3206 > intel_pt_process_auxtrace_info() warn: variable dereferenced before > check 'session->itrace_synth_opts' (see line 3200) > > tools/perf/util/intel-pt.c > 3196 if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > 3197 pt->synth_opts = *session->itrace_synth_opts; > 3198 } else { > 3199 itrace_synth_opts__set_default(&pt->synth_opts, > 3200 session->itrace_synth_opts->default_no_sample); > ^^^^^^^^^^^^^^^^^^^^^^^^^^ > 3201 if (!session->itrace_synth_opts->default_no_sample && > 3202 !session->itrace_synth_opts->inject) { > 3203 pt->synth_opts.branches = false; > 3204 pt->synth_opts.callchain = true; > 3205 } > 3206 if (session->itrace_synth_opts) > ^^^^^^^^^^^^^^^^^^^^^^^^^^ > 3207 pt->synth_opts.thread_stack = > 3208 session->itrace_synth_opts->thread_stack; > 3209 } > > 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/intel-pt.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c > index 550db6e77968..88b567bdf1f9 100644 > --- a/tools/perf/util/intel-pt.c > +++ b/tools/perf/util/intel-pt.c > @@ -3195,7 +3195,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event, > > if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > pt->synth_opts = *session->itrace_synth_opts; > - } else { > + } else if (session->itrace_synth_opts) { > itrace_synth_opts__set_default(&pt->synth_opts, > session->itrace_synth_opts->default_no_sample); > if (!session->itrace_synth_opts->default_no_sample && > @@ -3203,8 +3203,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event, > pt->synth_opts.branches = false; > pt->synth_opts.callchain = true; > } > - if (session->itrace_synth_opts) > - pt->synth_opts.thread_stack = > + pt->synth_opts.thread_stack = > session->itrace_synth_opts->thread_stack; > } > >
Hi Adrian, On Tue, Jul 02, 2019 at 02:07:40PM +0300, Adrian Hunter wrote: > On 2/07/19 1:34 PM, Leo Yan wrote: > > Based on the following report from Smatch, fix the potential > > NULL pointer dereference check. > > It never is NULL. Remove the NULL test if you want: > > - if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > + if (session->itrace_synth_opts->set) { > > But blindly making changes like below is questionable. Thanks for suggestions. I checked report and script commands, as you said, both command will always set session->itrace_synth_opts. For these two commands, we can safely remove the NULL test. Because perf tool contains many sub commands, so I don't have much confidence it's very safe to remove the NULL test for all cases; e.g. there have cases which will process aux trace buffer but without itrace options; for this case, session->itrace_synth_opts might be NULL. For either way (remove NULL test or keep NULL test), I don't want to introduce regression and extra efforts by my patch. So want to double confirm with you for this :) Thanks, Leo Yan > > tools/perf/util/intel-pt.c:3200 > > intel_pt_process_auxtrace_info() error: we previously assumed > > 'session->itrace_synth_opts' could be null (see line 3196) > > > > tools/perf/util/intel-pt.c:3206 > > intel_pt_process_auxtrace_info() warn: variable dereferenced before > > check 'session->itrace_synth_opts' (see line 3200) > > > > tools/perf/util/intel-pt.c > > 3196 if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > > 3197 pt->synth_opts = *session->itrace_synth_opts; > > 3198 } else { > > 3199 itrace_synth_opts__set_default(&pt->synth_opts, > > 3200 session->itrace_synth_opts->default_no_sample); > > ^^^^^^^^^^^^^^^^^^^^^^^^^^ > > 3201 if (!session->itrace_synth_opts->default_no_sample && > > 3202 !session->itrace_synth_opts->inject) { > > 3203 pt->synth_opts.branches = false; > > 3204 pt->synth_opts.callchain = true; > > 3205 } > > 3206 if (session->itrace_synth_opts) > > ^^^^^^^^^^^^^^^^^^^^^^^^^^ > > 3207 pt->synth_opts.thread_stack = > > 3208 session->itrace_synth_opts->thread_stack; > > 3209 } > > > > 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/intel-pt.c | 5 ++--- > > 1 file changed, 2 insertions(+), 3 deletions(-) > > > > diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c > > index 550db6e77968..88b567bdf1f9 100644 > > --- a/tools/perf/util/intel-pt.c > > +++ b/tools/perf/util/intel-pt.c > > @@ -3195,7 +3195,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event, > > > > if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > > pt->synth_opts = *session->itrace_synth_opts; > > - } else { > > + } else if (session->itrace_synth_opts) { > > itrace_synth_opts__set_default(&pt->synth_opts, > > session->itrace_synth_opts->default_no_sample); > > if (!session->itrace_synth_opts->default_no_sample && > > @@ -3203,8 +3203,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event, > > pt->synth_opts.branches = false; > > pt->synth_opts.callchain = true; > > } > > - if (session->itrace_synth_opts) > > - pt->synth_opts.thread_stack = > > + pt->synth_opts.thread_stack = > > session->itrace_synth_opts->thread_stack; > > } > > > > >
On 3/07/19 4:35 AM, Leo Yan wrote: > Hi Adrian, > > On Tue, Jul 02, 2019 at 02:07:40PM +0300, Adrian Hunter wrote: >> On 2/07/19 1:34 PM, Leo Yan wrote: >>> Based on the following report from Smatch, fix the potential >>> NULL pointer dereference check. >> >> It never is NULL. Remove the NULL test if you want: >> >> - if (session->itrace_synth_opts && session->itrace_synth_opts->set) { >> + if (session->itrace_synth_opts->set) { >> >> But blindly making changes like below is questionable. > > Thanks for suggestions. > > I checked report and script commands, as you said, both command will > always set session->itrace_synth_opts. For these two commands, we can > safely remove the NULL test. > > Because perf tool contains many sub commands, so I don't have much > confidence it's very safe to remove the NULL test for all cases; e.g. > there have cases which will process aux trace buffer but without > itrace options; for this case, session->itrace_synth_opts might be NULL. > > For either way (remove NULL test or keep NULL test), I don't want to > introduce regression and extra efforts by my patch. So want to double > confirm with you for this :) Yes, intel_pt_process_auxtrace_info() only gets called if a tool sets up the tools->auxtrace_info() callback. The tools that do that also set session->itrace_synth_opts.
On Wed, Jul 03, 2019 at 08:19:19AM +0300, Adrian Hunter wrote: > On 3/07/19 4:35 AM, Leo Yan wrote: > > Hi Adrian, > > > > On Tue, Jul 02, 2019 at 02:07:40PM +0300, Adrian Hunter wrote: > >> On 2/07/19 1:34 PM, Leo Yan wrote: > >>> Based on the following report from Smatch, fix the potential > >>> NULL pointer dereference check. > >> > >> It never is NULL. Remove the NULL test if you want: > >> > >> - if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > >> + if (session->itrace_synth_opts->set) { > >> > >> But blindly making changes like below is questionable. > > > > Thanks for suggestions. > > > > I checked report and script commands, as you said, both command will > > always set session->itrace_synth_opts. For these two commands, we can > > safely remove the NULL test. > > > > Because perf tool contains many sub commands, so I don't have much > > confidence it's very safe to remove the NULL test for all cases; e.g. > > there have cases which will process aux trace buffer but without > > itrace options; for this case, session->itrace_synth_opts might be NULL. > > > > For either way (remove NULL test or keep NULL test), I don't want to > > introduce regression and extra efforts by my patch. So want to double > > confirm with you for this :) > > Yes, intel_pt_process_auxtrace_info() only gets called if a tool sets up the > tools->auxtrace_info() callback. The tools that do that also set > session->itrace_synth_opts. Yes. I also checked the another case for 'perf inject', just as you said, it sets both inject->tool.auxtrace_info and session->itrace_synth_opts if we use 'itrace' option. So it's safe to remove the NULL test for session->itrace_synth_opts. Will follow your suggestion for new patches. Thanks a lot for confirmation and suggestions. Thanks, Leo Yan
On Wed, Jul 03, 2019 at 09:35:54AM +0800, Leo Yan wrote: > Hi Adrian, > > On Tue, Jul 02, 2019 at 02:07:40PM +0300, Adrian Hunter wrote: > > On 2/07/19 1:34 PM, Leo Yan wrote: > > > Based on the following report from Smatch, fix the potential > > > NULL pointer dereference check. > > > > It never is NULL. Remove the NULL test if you want: > > > > - if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > > + if (session->itrace_synth_opts->set) { > > > > But blindly making changes like below is questionable. > > Thanks for suggestions. > > I checked report and script commands, as you said, both command will > always set session->itrace_synth_opts. For these two commands, we can > safely remove the NULL test. > > Because perf tool contains many sub commands, so I don't have much > confidence it's very safe to remove the NULL test for all cases; e.g. > there have cases which will process aux trace buffer but without > itrace options; for this case, session->itrace_synth_opts might be NULL. > > For either way (remove NULL test or keep NULL test), I don't want to > introduce regression and extra efforts by my patch. So want to double > confirm with you for this :) Review is useful to ensure the chosen solution is correct but unless I missed something the non-regression reasoning here is easy easy. In its original form and despite the check, the code will always dereference session->itrace_synth_opts, therefore removing the check cannot makes things worse. Daniel. PS Of course we do also have to check that itrace_synth_opts__set_default() isn't a macro... but it isn't. > > > tools/perf/util/intel-pt.c:3200 > > > intel_pt_process_auxtrace_info() error: we previously assumed > > > 'session->itrace_synth_opts' could be null (see line 3196) > > > > > > tools/perf/util/intel-pt.c:3206 > > > intel_pt_process_auxtrace_info() warn: variable dereferenced before > > > check 'session->itrace_synth_opts' (see line 3200) > > > > > > tools/perf/util/intel-pt.c > > > 3196 if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > > > 3197 pt->synth_opts = *session->itrace_synth_opts; > > > 3198 } else { > > > 3199 itrace_synth_opts__set_default(&pt->synth_opts, > > > 3200 session->itrace_synth_opts->default_no_sample); > > > ^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > 3201 if (!session->itrace_synth_opts->default_no_sample && > > > 3202 !session->itrace_synth_opts->inject) { > > > 3203 pt->synth_opts.branches = false; > > > 3204 pt->synth_opts.callchain = true; > > > 3205 } > > > 3206 if (session->itrace_synth_opts) > > > ^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > 3207 pt->synth_opts.thread_stack = > > > 3208 session->itrace_synth_opts->thread_stack; > > > 3209 } > > > > > > 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/intel-pt.c | 5 ++--- > > > 1 file changed, 2 insertions(+), 3 deletions(-) > > > > > > diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c > > > index 550db6e77968..88b567bdf1f9 100644 > > > --- a/tools/perf/util/intel-pt.c > > > +++ b/tools/perf/util/intel-pt.c > > > @@ -3195,7 +3195,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event, > > > > > > if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > > > pt->synth_opts = *session->itrace_synth_opts; > > > - } else { > > > + } else if (session->itrace_synth_opts) { > > > itrace_synth_opts__set_default(&pt->synth_opts, > > > session->itrace_synth_opts->default_no_sample); > > > if (!session->itrace_synth_opts->default_no_sample && > > > @@ -3203,8 +3203,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event, > > > pt->synth_opts.branches = false; > > > pt->synth_opts.callchain = true; > > > } > > > - if (session->itrace_synth_opts) > > > - pt->synth_opts.thread_stack = > > > + pt->synth_opts.thread_stack = > > > session->itrace_synth_opts->thread_stack; > > > } > > > > > > > >
On Wed, Jul 03, 2019 at 11:00:32AM +0100, Daniel Thompson wrote: > On Wed, Jul 03, 2019 at 09:35:54AM +0800, Leo Yan wrote: > > Hi Adrian, > > > > On Tue, Jul 02, 2019 at 02:07:40PM +0300, Adrian Hunter wrote: > > > On 2/07/19 1:34 PM, Leo Yan wrote: > > > > Based on the following report from Smatch, fix the potential > > > > NULL pointer dereference check. > > > > > > It never is NULL. Remove the NULL test if you want: > > > > > > - if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > > > + if (session->itrace_synth_opts->set) { > > > > > > But blindly making changes like below is questionable. > > > > Thanks for suggestions. > > > > I checked report and script commands, as you said, both command will > > always set session->itrace_synth_opts. For these two commands, we can > > safely remove the NULL test. > > > > Because perf tool contains many sub commands, so I don't have much > > confidence it's very safe to remove the NULL test for all cases; e.g. > > there have cases which will process aux trace buffer but without > > itrace options; for this case, session->itrace_synth_opts might be NULL. > > > > For either way (remove NULL test or keep NULL test), I don't want to > > introduce regression and extra efforts by my patch. So want to double > > confirm with you for this :) > > Review is useful to ensure the chosen solution is correct but > unless I missed something the non-regression reasoning here is easy > easy. In its original form and despite the check, the code will > always dereference session->itrace_synth_opts, therefore removing > the check cannot makes things worse. Fair point and it's smart to connect with function itrace_synth_opts__set_default(). :) Thanks, Daniel. > PS Of course we do also have to check that > itrace_synth_opts__set_default() isn't a macro... but it isn't. > > > > > > tools/perf/util/intel-pt.c:3200 > > > > intel_pt_process_auxtrace_info() error: we previously assumed > > > > 'session->itrace_synth_opts' could be null (see line 3196) > > > > > > > > tools/perf/util/intel-pt.c:3206 > > > > intel_pt_process_auxtrace_info() warn: variable dereferenced before > > > > check 'session->itrace_synth_opts' (see line 3200) > > > > > > > > tools/perf/util/intel-pt.c > > > > 3196 if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > > > > 3197 pt->synth_opts = *session->itrace_synth_opts; > > > > 3198 } else { > > > > 3199 itrace_synth_opts__set_default(&pt->synth_opts, > > > > 3200 session->itrace_synth_opts->default_no_sample); > > > > ^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > > 3201 if (!session->itrace_synth_opts->default_no_sample && > > > > 3202 !session->itrace_synth_opts->inject) { > > > > 3203 pt->synth_opts.branches = false; > > > > 3204 pt->synth_opts.callchain = true; > > > > 3205 } > > > > 3206 if (session->itrace_synth_opts) > > > > ^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > > 3207 pt->synth_opts.thread_stack = > > > > 3208 session->itrace_synth_opts->thread_stack; > > > > 3209 } > > > > > > > > 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/intel-pt.c | 5 ++--- > > > > 1 file changed, 2 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c > > > > index 550db6e77968..88b567bdf1f9 100644 > > > > --- a/tools/perf/util/intel-pt.c > > > > +++ b/tools/perf/util/intel-pt.c > > > > @@ -3195,7 +3195,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event, > > > > > > > > if (session->itrace_synth_opts && session->itrace_synth_opts->set) { > > > > pt->synth_opts = *session->itrace_synth_opts; > > > > - } else { > > > > + } else if (session->itrace_synth_opts) { > > > > itrace_synth_opts__set_default(&pt->synth_opts, > > > > session->itrace_synth_opts->default_no_sample); > > > > if (!session->itrace_synth_opts->default_no_sample && > > > > @@ -3203,8 +3203,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event, > > > > pt->synth_opts.branches = false; > > > > pt->synth_opts.callchain = true; > > > > } > > > > - if (session->itrace_synth_opts) > > > > - pt->synth_opts.thread_stack = > > > > + pt->synth_opts.thread_stack = > > > > session->itrace_synth_opts->thread_stack; > > > > } > > > > > > > > > > >
diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c index 550db6e77968..88b567bdf1f9 100644 --- a/tools/perf/util/intel-pt.c +++ b/tools/perf/util/intel-pt.c @@ -3195,7 +3195,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event, if (session->itrace_synth_opts && session->itrace_synth_opts->set) { pt->synth_opts = *session->itrace_synth_opts; - } else { + } else if (session->itrace_synth_opts) { itrace_synth_opts__set_default(&pt->synth_opts, session->itrace_synth_opts->default_no_sample); if (!session->itrace_synth_opts->default_no_sample && @@ -3203,8 +3203,7 @@ int intel_pt_process_auxtrace_info(union perf_event *event, pt->synth_opts.branches = false; pt->synth_opts.callchain = true; } - if (session->itrace_synth_opts) - pt->synth_opts.thread_stack = + pt->synth_opts.thread_stack = session->itrace_synth_opts->thread_stack; }
Based on the following report from Smatch, fix the potential NULL pointer dereference check. tools/perf/util/intel-pt.c:3200 intel_pt_process_auxtrace_info() error: we previously assumed 'session->itrace_synth_opts' could be null (see line 3196) tools/perf/util/intel-pt.c:3206 intel_pt_process_auxtrace_info() warn: variable dereferenced before check 'session->itrace_synth_opts' (see line 3200) tools/perf/util/intel-pt.c 3196 if (session->itrace_synth_opts && session->itrace_synth_opts->set) { 3197 pt->synth_opts = *session->itrace_synth_opts; 3198 } else { 3199 itrace_synth_opts__set_default(&pt->synth_opts, 3200 session->itrace_synth_opts->default_no_sample); ^^^^^^^^^^^^^^^^^^^^^^^^^^ 3201 if (!session->itrace_synth_opts->default_no_sample && 3202 !session->itrace_synth_opts->inject) { 3203 pt->synth_opts.branches = false; 3204 pt->synth_opts.callchain = true; 3205 } 3206 if (session->itrace_synth_opts) ^^^^^^^^^^^^^^^^^^^^^^^^^^ 3207 pt->synth_opts.thread_stack = 3208 session->itrace_synth_opts->thread_stack; 3209 } 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/intel-pt.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)