linux-kernel - Re: [PATCH] perf hists browser: Fix segfault when all entries be filtered

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Date:	Tue, 10 Mar 2015 15:01:12 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	He Kuang <hekuang@...wei.com>
Cc:	acme@...nel.org, a.p.zijlstra@...llo.nl, mingo@...hat.com,
	paulus@...ba.org, jolsa@...nel.org, wangnan0@...wei.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf hists browser: Fix segfault when all entries be
 filtered

Hi,

On Tue, Mar 10, 2015 at 11:38:59AM +0800, He Kuang wrote:
> ping..
> On 2015/3/4 12:13, He Kuang wrote:
> >When all perf report entries be filtered, the result of
> >hists__filter_entries() can be NULL, check the result before processing.

In that case, browser->nr_entries should be zero IMHO.  But it seems
there's a place missing to update the number.

Thanks,
Namhyung


> >
> >Miss this checking will cause segmentation fault like this:
> >
> >   $ perf report
> >
> >(filter all entries and left nothing, then zoom in/out)
> >   perf: Segmentation fault
> >   -------- backtrace --------
> >   ../bin/perf[0x4d1858]
> >   ../lib64/libc.so.6(+0x3545f)[0x7fe72fc1145f]
> >   ../bin/perf[0x4cd9f5]
> >   ../bin/perf[0x4ce176]
> >   ../bin/perf[0x4d0506]
> >   ../bin/perf[0x41a94f]
> >   ../bin/perf[0x408cf2]
> >   ../bin/perf[0x408455]
> >   ../lib64/libc.so.6(__libc_start_main+0xf4)[0x7fe72fbfdbd4]
> >   ../bin/perf[0x408584]
> >
> >Signed-off-by: He Kuang <hekuang@...wei.com>
> >---
> >  tools/perf/ui/browsers/hists.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> >diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
> >index 788506e..1106bb8 100644
> >--- a/tools/perf/ui/browsers/hists.c
> >+++ b/tools/perf/ui/browsers/hists.c
> >@@ -992,6 +992,9 @@ static void ui_browser__hists_seek(struct ui_browser *browser,
> >  	 * and stop when we printed enough lines to fill the screen.
> >  	 */
> >  do_offset:
> >+	if (!nd)
> >+		return;
> >+
> >  	if (offset > 0) {
> >  		do {
> >  			h = rb_entry(nd, struct hist_entry, rb_node);
> 
> 
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