[3/5] perf hists browser: Add NULL pointer check to prevent crash

Message ID 1449518801-18511-4-git-send-email-acme@kernel.org
State New
Headers show

Commit Message

Arnaldo Carvalho de Melo Dec. 7, 2015, 8:06 p.m.
From: Wang Nan <wangnan0@huawei.com>

Before this patch we can trigger a segfault by following steps:

 Step 0: Use 'perf record' to generate a perf.data without callchain

 Step 1: perf report

 Step 2: Use UP/DOWN to select an entry, don't press 'ENTER'

 Step 3: Use '/' to filter symbols, use a filter which returns
         empty result

 Step 4: Press 'ENTER' (notice here that the old selection is still
		        there. This is another problem)

 Step 5: Press 'ENTER' to annotate that symbol

 Step 6: Press 'LEFT' to go out.

 Result: segfault:

 perf: Segmentation fault
 -------- backtrace --------

This is because in this case 'nd' could be NULL in
ui_browser__hists_seek(), but that function never checks it.

This patch adds checker for potential NULL pointer in that function.
After this patch the above steps won't segfault.

Signed-off-by: Wang Nan <wangnan0@huawei.com>

Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1449455746-41952-3-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

 tools/perf/ui/browsers/hists.c | 3 +++
 1 file changed, 3 insertions(+)


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diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
index fa9eb92c9e24..932e13d015b9 100644
--- a/tools/perf/ui/browsers/hists.c
+++ b/tools/perf/ui/browsers/hists.c
@@ -1033,6 +1033,9 @@  static void ui_browser__hists_seek(struct ui_browser *browser,
 	 * and stop when we printed enough lines to fill the screen.
+	if (!nd)
+		return;
 	if (offset > 0) {
 		do {
 			h = rb_entry(nd, struct hist_entry, rb_node);