perf auxtrace: Fix potential NULL pointer dereference

In the function auxtrace_parse_snapshot_options(), the callback pointer
"itr->parse_snapshot_options" can be NULL if it has not been set during
the AUX record initialization.  This can cause tool crashing if the
callback pointer "itr->parse_snapshot_options" is dereferenced without
performing NULL check.

Add a NULL check for the pointer "itr->parse_snapshot_options" before
invoke the callback.

Fixes: d20031b ("perf tools: Add AUX area tracing Snapshot Mode")
Signed-off-by: Leo Yan <[email protected]>
Acked-by: Adrian Hunter <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Tiezhu Yang <[email protected]>
Link: http://lore.kernel.org/lkml/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: Leo Yan

tools/perf/util/auxtrace.c

@@ -634,7 +634,7 @@ int auxtrace_parse_snapshot_options(struct auxtrace_record *itr,
 		break;
 	}
 
-	if (itr)
+	if (itr && itr->parse_snapshot_options)
 		return itr->parse_snapshot_options(itr, opts, str);
 
 	pr_err("No AUX area tracing to snapshot\n");