perf trace: Fix read_string()

We did not account for the enclosing \0. Depending on what malloc()
gave us this resulted in corrupted version string printouts.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/util/trace-event-read.c

@@ -113,8 +113,11 @@ static char *read_string(void)
 		}
 	}
 
+	/* trailing \0: */
+	i++;
+
 	/* move the file descriptor to the end of the string */
-	r = lseek(input_fd, -(r - (i+1)), SEEK_CUR);
+	r = lseek(input_fd, -(r - i), SEEK_CUR);
 	if (r < 0)
 		die("lseek");