filesystem_freebsd: Fix label values

We must know the length of the various filesystem C strings before
turning them from a byte array into a Go string, otherwise our Go
strings could contain null bytes, corrupting the label values.

Signed-off-by: David O'Rourke <david.orourke@gmail.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/collector/filesystem_freebsd.go b/collector/filesystem_freebsd.go
index f37029e..8bc8314 100644
--- a/collector/filesystem_freebsd.go
+++ b/collector/filesystem_freebsd.go
@@ -16,6 +16,8 @@
 package collector
 
 import (
+        "bytes"
+
         "github.com/go-kit/kit/log/level"
         "golang.org/x/sys/unix"
 )
@@ -40,14 +42,19 @@ func (c *filesystemCollector) GetStats() ([]filesystemStats, error) {
         }
         stats := []filesystemStats{}
         for _, fs := range buf {
-                mountpoint := string(fs.Mntonname[:])
+                // We need to work out the lengths of the actual strings here,
+                // otherwuse we will end up with null bytes in our label values.
+                mountpoint_len := bytes.Index(fs.Mntonname[:], []byte{0})
+                mountpoint := string(fs.Mntonname[:mountpoint_len])
                 if c.ignoredMountPointsPattern.MatchString(mountpoint) {
                         level.Debug(c.logger).Log("msg", "Ignoring mount point", "mountpoint", mountpoint)
                         continue
                 }
 
-                device := string(fs.Mntfromname[:])
-                fstype := string(fs.Fstypename[:])
+                device_len := bytes.Index(fs.Mntfromname[:], []byte{0})
+                fstype_len := bytes.Index(fs.Fstypename[:], []byte{0})
+                device := string(fs.Mntfromname[:device_len])
+                fstype := string(fs.Fstypename[:fstype_len])
                 if c.ignoredFSTypesPattern.MatchString(fstype) {
                         level.Debug(c.logger).Log("msg", "Ignoring fs type", "type", fstype)
                         continue