disk: guard against nil pointer dereferencing

Add guards protecting against dereferencing the pointer receiver of
method calls.

Co-Authored-By: Achilleas Koutsou <achilleas@koutsou.net>

internal/disk/btrfs.go

@@ -105,6 +105,9 @@ func (bs *BtrfsSubvolume) Clone() Entity {
 }
 
 func (bs *BtrfsSubvolume) GetSize() uint64 {
+	if bs == nil {
+		return 0
+	}
 	return bs.Size
 }
 
@@ -117,6 +120,9 @@ func (bs *BtrfsSubvolume) EnsureSize(s uint64) bool {
 }
 
 func (bs *BtrfsSubvolume) GetMountpoint() string {
+	if bs == nil {
+		return ""
+	}
 	return bs.Mountpoint
 }
 
@@ -125,6 +131,9 @@ func (bs *BtrfsSubvolume) GetFSType() string {
 }
 
 func (bs *BtrfsSubvolume) GetFSSpec() FSSpec {
+	if bs == nil {
+		return FSSpec{}
+	}
 	return FSSpec{
 		UUID:  bs.UUID,
 		Label: bs.Name,
@@ -132,8 +141,11 @@ func (bs *BtrfsSubvolume) GetFSSpec() FSSpec {
 }
 
 func (bs *BtrfsSubvolume) GetFSTabOptions() FSTabOptions {
-	ops := strings.Join([]string{bs.MntOps, fmt.Sprintf("subvol=%s", bs.Name)}, ",")
+	if bs == nil {
+		return FSTabOptions{}
+	}
 
+	ops := strings.Join([]string{bs.MntOps, fmt.Sprintf("subvol=%s", bs.Name)}, ",")
 	return FSTabOptions{
 		MntOps: ops,
 		Freq:   0,

internal/disk/disk.go

@@ -24,8 +24,6 @@ import (
 	"github.com/google/uuid"
 )
 
-// TODO: guard against nil dereferencing in pointer methods
-
 const (
 	// Default sector size in bytes
 	DefaultSectorSize = 512

internal/disk/filesystem.go

@@ -44,14 +44,23 @@ func (fs *Filesystem) Clone() Entity {
 }
 
 func (fs *Filesystem) GetMountpoint() string {
+	if fs == nil {
+		return ""
+	}
 	return fs.Mountpoint
 }
 
 func (fs *Filesystem) GetFSType() string {
+	if fs == nil {
+		return ""
+	}
 	return fs.Type
 }
 
 func (fs *Filesystem) GetFSSpec() FSSpec {
+	if fs == nil {
+		return FSSpec{}
+	}
 	return FSSpec{
 		UUID:  fs.UUID,
 		Label: fs.Label,
@@ -59,6 +68,9 @@ func (fs *Filesystem) GetFSSpec() FSSpec {
 }
 
 func (fs *Filesystem) GetFSTabOptions() FSTabOptions {
+	if fs == nil {
+		return FSTabOptions{}
+	}
 	return FSTabOptions{
 		MntOps: fs.FSTabOptions,
 		Freq:   fs.FSTabFreq,

internal/disk/luks.go

@@ -66,6 +66,10 @@ func (lc *LUKSContainer) Clone() Entity {
 }
 
 func (lc *LUKSContainer) GenUUID(rng *rand.Rand) {
+	if lc == nil {
+		return
+	}
+
 	if lc.UUID == "" {
 		lc.UUID = uuid.Must(newRandomUUIDFromReader(rng)).String()
 	}

internal/disk/lvm.go

@@ -41,14 +41,23 @@ func (vg *LVMVolumeGroup) Clone() Entity {
 }
 
 func (vg *LVMVolumeGroup) GetItemCount() uint {
+	if vg == nil {
+		return 0
+	}
 	return uint(len(vg.LogicalVolumes))
 }
 
 func (vg *LVMVolumeGroup) GetChild(n uint) Entity {
+	if vg == nil {
+		panic("LVMVolumeGroup.GetChild: nil entity")
+	}
 	return &vg.LogicalVolumes[n]
 }
 
 func (vg *LVMVolumeGroup) CreateVolume(mountpoint string, size uint64) (Entity, error) {
+	if vg == nil {
+		panic("LVMVolumeGroup.CreateVolume: nil entity")
+	}
 	filesystem := Filesystem{
 		Type:         "xfs",
 		Mountpoint:   mountpoint,
@@ -78,6 +87,9 @@ func (lv *LVMLogicalVolume) IsContainer() bool {
 }
 
 func (lv *LVMLogicalVolume) Clone() Entity {
+	if lv == nil {
+		return nil
+	}
 	return &LVMLogicalVolume{
 		Name:    lv.Name,
 		Size:    lv.Size,
@@ -86,24 +98,30 @@ func (lv *LVMLogicalVolume) Clone() Entity {
 }
 
 func (lv *LVMLogicalVolume) GetItemCount() uint {
-	if lv.Payload == nil {
+	if lv == nil || lv.Payload == nil {
 		return 0
 	}
 	return 1
 }
 
 func (lv *LVMLogicalVolume) GetChild(n uint) Entity {
-	if n != 0 {
+	if n != 0 || lv == nil {
 		panic(fmt.Sprintf("invalid child index for LVMLogicalVolume: %d != 0", n))
 	}
 	return lv.Payload
 }
 
 func (lv *LVMLogicalVolume) GetSize() uint64 {
+	if lv == nil {
+		return 0
+	}
 	return lv.Size
 }
 
 func (lv *LVMLogicalVolume) EnsureSize(s uint64) bool {
+	if lv == nil {
+		panic("LVMLogicalVolume.EnsureSize: nil entity")
+	}
 	if s > lv.Size {
 		lv.Size = s
 		return true

internal/disk/partition.go

@@ -24,7 +24,7 @@ func (p *Partition) IsContainer() bool {
 
 func (p *Partition) Clone() Entity {
 	if p == nil {
-		return p
+		return nil
 	}
 
 	ent := p.Payload.Clone()
@@ -48,7 +48,7 @@ func (p *Partition) Clone() Entity {
 }
 
 func (pt *Partition) GetItemCount() uint {
-	if pt.Payload == nil {
+	if pt == nil || pt.Payload == nil {
 		return 0
 	}
 	return 1