perf_counter tools: fix buffer overwrite problem for perf top command

There is a buffer overwrite problem in builtin-top.c line 526, When I
tried to use ./perf top command, it was giving memory corruption
problem.

[ Impact: fix 'perf top' crash ]

LKML-Reference: <3fee128b0905092313x608e65e0l7b1116d86914114f@mail.gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Documentation/perf_counter/builtin-top.c

@@ -523,7 +523,7 @@ static int read_symbol(FILE *in, struct sym_entry *s)
 	if (strstr(sym, "_text_start") || strstr(sym, "_text_end"))
 		return 1;
 
-	s->sym = malloc(strlen(str));
+	s->sym = malloc(strlen(str)+1);
 	assert(s->sym);
 
 	strcpy((char *)s->sym, str);