Re: [PATCH v2] perf tools: Fix segfault in 'perf top'

[Arnaldo Carvalho de Melo]

Em Mon, Sep 14, 2015 at 10:23:55AM +0000, Wang Nan escreveu:
> 'perf top' segfaults with following operation:
> 
>  # perf top -e page-faults -p 11400 # 11400 never generates page-fault
> 
> Then on the resulting empty interface, press right key:

So, this happens in perf/urgent, so we need to apply it there first,
which this patch doesn't.

I am fixing it up this time, thanks for the patch!

- Arnaldo
 
>  # ./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 checking browser->selection before fetching
> browser->selection->map.
> 
> Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> ---
>  tools/perf/ui/browsers/hists.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
> index e4fd40f..182b87a 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);
> @@ -2027,6 +2028,15 @@ skip_annotation:
>  						     &actions[nr_options],
>  						     &options[nr_options],
>  						     thread, NULL);
> +			/*
> +			 * Note that browser->selection != NULL
> +			 * when browser->he_selection is not NULL,
> +			 * so we don't need to check browser->selection
> +			 * before fetching browser->selection->sym like what
> +			 * we do before fetching browser->selection->map.
> +			 *
> +			 * See hist_browser__show_entry.
> +			 */
>  			nr_options += add_script_opt(browser,
>  						     &actions[nr_options],
>  						     &options[nr_options],
> -- 
> 1.8.3.4
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