perf utils: use sizeof(buf) - 1 in readlink() call

Ensure that we have space for the null byte in buf.

Signed-off-by: Tommi Rantala <tommi.t.rantala@nokia.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170322130624.21881-5-tommi.t.rantala@nokia.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 05714d5..cf22962 100644 (file)
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -378,7 +378,7 @@ static int write_cmdline(int fd, struct perf_header *h __maybe_unused,
         * actual atual path to perf binary
         */
        sprintf(proc, "/proc/%d/exe", getpid());
-       ret = readlink(proc, buf, sizeof(buf));
+       ret = readlink(proc, buf, sizeof(buf) - 1);
        if (ret <= 0)
                return -1;