Merge pull request #220 from amshinde/revert-dev-mount

Handle device nodes and regular files in /dev

virtcontainers/container.go

@@ -290,7 +290,7 @@ func (c *Container) createContainersDirs() error {
 func (c *Container) mountSharedDirMounts(hostSharedDir, guestSharedDir string) ([]Mount, error) {
 	var sharedDirMounts []Mount
 	for idx, m := range c.mounts {
-		if m.Type != "bind" {
+		if isSystemMount(m.Destination) || m.Type != "bind" {
 			continue
 		}
 
@@ -327,6 +327,13 @@ func (c *Container) mountSharedDirMounts(hostSharedDir, guestSharedDir string) (
 			continue
 		}
 
+		// Ignore /dev, directories and all other device files. We handle
+		// only regular files in /dev. It does not make sense to pass the host
+		// device nodes to the guest.
+		if isHostDevice(m.Destination) {
+			continue
+		}
+
 		randBytes, err := generateRandomBytes(8)
 		if err != nil {
 			return nil, err

virtcontainers/mount.go

@@ -18,6 +18,46 @@ import (
 
 var rootfsDir = "rootfs"
 
+var systemMountPrefixes = []string{"/proc", "/sys"}
+
+func isSystemMount(m string) bool {
+	for _, p := range systemMountPrefixes {
+		if m == p || strings.HasPrefix(m, p+"/") {
+			return true
+		}
+	}
+
+	return false
+}
+
+func isHostDevice(m string) bool {
+	if m == "/dev" {
+		return true
+	}
+
+	if strings.HasPrefix(m, "/dev/") {
+		// Check if regular file
+		s, err := os.Stat(m)
+
+		// This should not happen. In case file does not exist let the
+		// error be handled by the agent, simply return false here.
+		if err != nil {
+			return false
+		}
+
+		if s.Mode().IsRegular() {
+			return false
+		}
+
+		// This is not a regular file in /dev. It is either a
+		// device file, directory or any other special file which is
+		// specific to the host system.
+		return true
+	}
+
+	return false
+}
+
 func major(dev uint64) int {
 	return int((dev >> 8) & 0xfff)
 }

virtcontainers/mount_test.go

@@ -18,6 +18,66 @@ import (
 	"testing"
 )
 
+func TestIsSystemMount(t *testing.T) {
+	tests := []struct {
+		mnt      string
+		expected bool
+	}{
+		{"/sys", true},
+		{"/sys/", true},
+		{"/sys//", true},
+		{"/sys/fs", true},
+		{"/sys/fs/", true},
+		{"/sys/fs/cgroup", true},
+		{"/sysfoo", false},
+		{"/home", false},
+		{"/dev/block/", false},
+		{"/mnt/dev/foo", false},
+	}
+
+	for _, test := range tests {
+		result := isSystemMount(test.mnt)
+		if result != test.expected {
+			t.Fatalf("Expected result for path %s : %v, got %v", test.mnt, test.expected, result)
+		}
+	}
+}
+
+func TestIsHostDevice(t *testing.T) {
+	tests := []struct {
+		mnt      string
+		expected bool
+	}{
+		{"/dev", true},
+		{"/dev/zero", true},
+		{"/dev/block", true},
+		{"/mnt/dev/block", false},
+	}
+
+	for _, test := range tests {
+		result := isHostDevice(test.mnt)
+		if result != test.expected {
+			t.Fatalf("Expected result for path %s : %v, got %v", test.mnt, test.expected, result)
+		}
+	}
+
+	// Create regular file in /dev
+	path := "/dev/foobar"
+	f, err := os.Create(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	f.Close()
+
+	if isHostDevice(path) != false {
+		t.Fatalf("Expected result for path %s : %v, got %v", path, false, true)
+	}
+
+	if err := os.Remove(path); err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestMajorMinorNumber(t *testing.T) {
 	devices := []string{"/dev/zero", "/dev/net/tun"}