perf annotate: Fix heap overflow

Fix expand_tabs that copies the source lines '\0' and then appends
another '\0' at a potentially out of bounds address.

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20191026035644.217548-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/annotate.c

@@ -1892,7 +1892,7 @@ static char *expand_tabs(char *line, char **storage, size_t *storage_len)
 	}
 
 	/* Expand the last region. */
-	len = line_len + 1 - src;
+	len = line_len - src;
 	memcpy(&new_line[dst], &line[src], len);
 	dst += len;
 	new_line[dst] = '\0';