tools lib traceevent: Do not free tep->cmdlines in add_new_comm() on failure

BugLink: https://bugs.launchpad.net/bugs/1848780

[ Upstream commit e0d2615856b2046c2e8d5bfd6933f37f69703b0b ]

If the re-allocation of tep->cmdlines succeeds, then the previous
allocation of tep->cmdlines will be freed. If we later fail in
add_new_comm(), we must not free cmdlines, and also should assign
tep->cmdlines to the new allocation. Otherwise when freeing tep, the
tep->cmdlines will be pointing to garbage.

Fixes: a6d2a61a ("tools lib traceevent: Remove some die() calls")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: linux-trace-devel@vger.kernel.org
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20190828191819.970121417@goodmis.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

tools/lib/traceevent/event-parse.c

@@ -265,10 +265,10 @@ static int add_new_comm(struct pevent *pevent, const char *comm, int pid)
 		errno = ENOMEM;
 		return -1;
 	}
+	pevent->cmdlines = cmdlines;
 
 	cmdlines[pevent->cmdline_count].comm = strdup(comm);
 	if (!cmdlines[pevent->cmdline_count].comm) {
-		free(cmdlines);
 		errno = ENOMEM;
 		return -1;
 	}
@@ -279,7 +279,6 @@ static int add_new_comm(struct pevent *pevent, const char *comm, int pid)
 		pevent->cmdline_count++;
 
 	qsort(cmdlines, pevent->cmdline_count, sizeof(*cmdlines), cmdline_cmp);
-	pevent->cmdlines = cmdlines;
 
 	return 0;
 }