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

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Date:	Thu, 3 Dec 2015 10:19:36 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Namhyung Kim <namhyung@...nel.org>
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



On 2015/12/2 23:49, Namhyung Kim wrote:
> 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.

I know it. Add it only for correctness.

Will be removed.

Thank you.

> 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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