linux-kernel - Re: [PATCH] perf hists browser: Fix segfault if use symbol filter in cmdline

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Date:	Thu, 3 Dec 2015 00:49:42 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	acme@...nel.org, lizefan@...wei.com, pi3orama@....com,
	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH] perf hists browser: Fix segfault if use symbol filter in
 cmdline

Hi,

On Wed, Dec 02, 2015 at 11:28:52AM +0000, Wang Nan wrote:
> If feed perf a symbol filter in cmdline and the result is empty,
> pressing 'Enter' in the hist browser causes crash:
> 
>  # ./perf report perf.data   <-- Common mistake for beginners
> 
> Then press 'Enter':
> 
>  perf: Segmentation fault
>  -------- backtrace --------
>  /home/wangnan/perf[0x53e578]
>  /lib64/libc.so.6(+0x3545f)[0x7f76bafe045f]
>  /home/wangnan/perf[0x539dd4]
>  /home/wangnan/perf(perf_evlist__tui_browse_hists+0x96)[0x53d216]
>  /home/wangnan/perf(cmd_report+0x1b9f)[0x442c7f]
>  /home/wangnan/perf[0x47efa2]
>  /home/wangnan/perf(main+0x5f5)[0x432fa5]
>  /lib64/libc.so.6(__libc_start_main+0xf4)[0x7f76bafccbd4]
>  /home/wangnan/perf[0x4330d4]
> 
> This is because 'perf.data' is interperted as a symbol filter, and the
> result is empty, so selection is empty. However,
> hist_browser__toggle_fold() forgets to check it.
> 
> This patch simply return faluse when selection is NULL.

s/faluse/false/

> 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>

Acked-by: Namhyung Kim <namhyung@...nel.org>

One nitpick below..

> ---
>  tools/perf/ui/browsers/hists.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
> index dcdcbaf..33da341 100644
> --- a/tools/perf/ui/browsers/hists.c
> +++ b/tools/perf/ui/browsers/hists.c
> @@ -337,9 +337,12 @@ static bool hist_browser__toggle_fold(struct hist_browser *browser)
>  {
>  	struct hist_entry *he = browser->he_selection;
>  	struct map_symbol *ms = browser->selection;
> -	struct callchain_list *cl = container_of(ms, struct callchain_list, ms);
> +	struct callchain_list *cl = ms ? container_of(ms, struct callchain_list, ms) : NULL;

I think this line is not needed as container_of doesn't make a pointer
dereference by itself.  Just checking below is enough IMHO.

Thanks,
Namhyung


>  	bool has_children;
>  
> +	if (!ms)
> +		return false;
> +
>  	if (ms == &he->ms)
>  		has_children = hist_entry__toggle_fold(he);
>  	else
> -- 
> 1.8.3.4
> 
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