perf tools: Do not accept parse_tag_value() overflow

parse_tag_value() accepts an "unsigned long" and multiplies it according
to a tag character.  Do not accept the value if the multiplication
overflows.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1382427258-17495-14-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/util.c

@@ -386,6 +386,8 @@ unsigned long parse_tag_value(const char *str, struct parse_tag *tags)
 			if (s != endptr)
 				break;
 
+			if (value > ULONG_MAX / i->mult)
+				break;
 			value *= i->mult;
 			return value;
 		}