Messages in this thread | | | Date | Mon, 14 Sep 2015 18:15:22 +0800 | From | "Wangnan (F)" <> | Subject | Re: [PATCH] perf tools: Fix segfault in 'perf top' |
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On 2015/9/12 0:22, Namhyung Kim wrote: > On Fri, Sep 11, 2015 at 04:59:11AM +0000, Wang Nan wrote: >> 'perf top' segfaults with following operation: >> >> # perf top -e page-faults -p 15173 # 15173 never generate page-fault >> >> Then on the resulting empty interface, press right key: >> >> # ./perf top -e page-faults -p 11400 >> perf: Segmentation fault >> -------- backtrace -------- >> ./perf[0x535428] >> /lib64/libc.so.6(+0x3545f)[0x7f0dd360745f] >> ./perf[0x531d46] >> ./perf(perf_evlist__tui_browse_hists+0x96)[0x5340d6] >> ./perf[0x44ba2f] >> /lib64/libpthread.so.0(+0x81d0)[0x7f0dd49dc1d0] >> /lib64/libc.so.6(clone+0x6c)[0x7f0dd36b90dc] >> >> The bug reside in perf_evsel__hists_browse() that, in the above circumstance >> browser->selection can be NULL, but code after skip_annotation doesn't consider >> it. >> >> This patch fix it by checing browser->selection before fetching >> browser->selection->map and browser->selection->sym. > I'm ok with this change, just a nitpick below.. > > >> Signed-off-by: Wang Nan <wangnan0@huawei.com> >> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> >> Cc: Namhyung Kim <namhyung@kernel.org> >> --- >> tools/perf/ui/browsers/hists.c | 8 ++++++-- >> 1 file changed, 6 insertions(+), 2 deletions(-) >> >> diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c >> index e4fd40f..b00fa92 100644 >> --- a/tools/perf/ui/browsers/hists.c >> +++ b/tools/perf/ui/browsers/hists.c >> @@ -2017,7 +2017,8 @@ skip_annotation: >> &options[nr_options], dso); >> nr_options += add_map_opt(browser, &actions[nr_options], >> &options[nr_options], >> - browser->selection->map); >> + browser->selection ? >> + browser->selection->map : NULL); >> nr_options += add_socket_opt(browser, &actions[nr_options], >> &options[nr_options], >> socket); >> @@ -2030,7 +2031,10 @@ skip_annotation: >> nr_options += add_script_opt(browser, >> &actions[nr_options], >> &options[nr_options], >> - NULL, browser->selection->sym); >> + NULL, >> + browser->selection ? >> + browser->selection->sym : >> + NULL); > Is this really needed? IIUC browser->selection is not NULL if > browser->he_selection is not NULL. Did you see a case it's NULL? > Also passing a NULL thread and a NULL sym is meaningless here since > it's a duplication..
Actually I didn't see the case when browser->he_selection is not NULL but browser->selection is NULL. I add the testing only for safety reason because we have
if (browser->selection == NULL) goto skip_annotation;
So I guess we'd better to check browser->selection in the codeblock leading by skip_annotation, so if someone breaks the assumption the code still work.
But yes, we can add the checker back when the assumption *does* be broken. Currently let's add a comment here for code readers.
Please have a look for v2 patch.
Thank you.
> Thanks, > Namhyung > > >> } >> nr_options += add_script_opt(browser, &actions[nr_options], >> &options[nr_options], NULL, NULL); >> -- >> 1.8.3.4 >>
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