[PATCH] tools: perf: session: avoid segfault on implicit stdin

[PATCH] tools: perf: session: avoid segfault on implicit stdin

[Stephen Brennan]

A user reported that running a command like:

    perf script flamegraph -ag -F99 -- sleep 10

Resulted in a segmentation fault. The reason is twofold. First, the
"flamegraph-report" script has a shebang line which ends with "--". This
disables option parsing, so that the exec'd "perf script report" command
does not see the option "-i -" which is appended to its command line.
Second, despite the unprocessed "-i -" option, the default behavior of
perf is to use stdin if it is a pipe -- and in this case, it is. Thus, the
report continues running, but segfaults on accessing the filename.

The fix for the second issue is a simple NULL check. Implement this
here.

Fixes: 4553c431e7dd2 ("perf report: Display pregress bar on redirected pipe data")

Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com>
---
 tools/perf/util/session.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 26ae078278cd6..a9624505c0ca3 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1854,9 +1854,11 @@ static int __perf_session__process_pipe_events(struct perf_session *session)
 	/*
 	 * If it's from a file saving pipe data (by redirection), it would have
 	 * a file name other than "-".  Then we can get the total size and show
-	 * the progress.
+	 * the progress. However, be careful because path may be NULL if input
+	 * is coming from stdin.
 	 */
-	if (strcmp(session->data->path, "-") && session->data->file.size) {
+	if (session->data->path && strcmp(session->data->path, "-")
+	    && session->data->file.size) {
 		ui_progress__init_size(&prog, session->data->file.size,
 				       "Processing events...");
 		update_prog = true;
-- 
2.47.3