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Subjectlinux-perf-5.2: perf report: segmentation fault accessing browser->he_selection
Date
Hello,
in Debian bug [943398] another user reported a crash of the
perf application. I tried triaging the issue.

I could reproduce the issue using linux-perf-5.2
and it is also visible in linux-perf-5.4 5.4.8-1

With following commands:

perf record ls
perf report perf.data
# Press enter

The crash happens because in line 3172
function hist_browser__selected_entry returns
browser->he_selection, which is at this time a
null pointer.
This null pointer gets dereferenced to
access the res_samples member.

Other occourences of browser->he_selection being null
seem to get fixed in [1], but this is
already contained in 5.4 while a crash still happens.

It got reported to be visible also in 5.5~rc5.

Kind regards,
Bernhard



Program received signal SIGSEGV, Segmentation fault.
(rr) bt
#0 perf_evsel__hists_browse (evsel=0x55e794ebcb40, nr_events=nr_events@entry=1, helpline=helpline@entry=0x55e794f7c040 "Tip: System-wide collection from all CPUs: perf record -a", left_exits=left_exits@entry=false, hbt=hbt@entry=0x0, min_pcnt=<optimized out>, env=env@entry=0x55e794eb54f0, warn_lost_event=true, annotation_opts=0x7ffcc3063dc8) at ui/browsers/hists.c:3170
#1 0x000055e79385cce9 in perf_evlist__tui_browse_hists (evlist=evlist@entry=0x55e794ebc0c0, help=help@entry=0x55e794f7c040 "Tip: System-wide collection from all CPUs: perf record -a", hbt=hbt@entry=0x0, min_pcnt=<optimized out>, env=env@entry=0x55e794eb54f0, warn_lost_event=warn_lost_event@entry=true, annotation_opts=annotation_opts@entry=0x7ffcc3063dc8) at ui/browsers/hists.c:3422
#2 0x000055e7936f1ece in report__browse_hists (rep=0x7ffcc3063c30) at builtin-report.c:585
#3 __cmd_report (rep=0x7ffcc3063c30) at builtin-report.c:930
#4 cmd_report (argc=<optimized out>, argv=<optimized out>) at builtin-report.c:1475
#5 0x000055e79375b823 in run_builtin (p=0x55e793a9ef90 <commands+240>, argc=2, argv=0x7ffcc30661f0) at perf.c:312
#6 0x000055e7936d6a2c in handle_internal_command (argv=<optimized out>, argc=<optimized out>) at perf.c:364
#7 run_argv (argcp=<optimized out>, argv=<optimized out>) at perf.c:408
#8 main (argc=2, argv=0x7ffcc30661f0) at perf.c:538


https://sources.debian.org/src/linux/5.4.8-1/tools/perf/ui/browsers/hists.c/#L2217
2217 static struct hist_entry *hist_browser__selected_entry(struct hist_browser *browser)
2218 {
2219 return browser->he_selection;
2220 }

https://sources.debian.org/src/linux/5.4.8-1/tools/perf/ui/browsers/hists.c/#L3170
3170 nr_options += add_res_sample_opt(browser, &actions[nr_options],
3171 &options[nr_options],
3172 hist_browser__selected_entry(browser)->res_samples,
3173 evsel, A_NORMAL);



[943398] https://bugs.debian.org/943398
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/tools/perf/ui/browsers/hists.c?id=ceb75476db1617a88cc29b09839acacb69aa076e

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