Remove references to replaced child in Rename in ramfs/agentfs

In the case of a rename replacing an existing destination inode, ramfs
Rename failed to first remove the replaced inode. This caused:

1. A leak of a reference to the inode (making it live indefinitely).
2. For directories, a leak of the replaced directory's .. link to the
   parent. This would cause the parent's link count to incorrectly
   increase.

(2) is much simpler to test than (1), so that's what I've done.

agentfs has a similar bug with link count only, so the Dirent layer
informs the Inode if this is a replacing rename.

Fixes #133

PiperOrigin-RevId: 239105698
Change-Id: I4450af2462d8ae3339def812287213d2cbeebde0

2 files changed, 12 insertions, 12 deletions

diff --git a/pkg/sentry/fs/tmpfs/inode_file.go b/pkg/sentry/fs/tmpfs/inode_file.go
index a98fbf0f1..3c84b2977 100644
--- a/pkg/sentry/fs/tmpfs/inode_file.go
+++ b/pkg/sentry/fs/tmpfs/inode_file.go
@@ -107,8 +107,8 @@ func (f *fileInodeOperations) Mappable(*fs.Inode) memmap.Mappable {
 }
 
 // Rename implements fs.InodeOperations.Rename.
-func (*fileInodeOperations) Rename(ctx context.Context, oldParent *fs.Inode, oldName string, newParent *fs.Inode, newName string) error {
-	return rename(ctx, oldParent, oldName, newParent, newName)
+func (*fileInodeOperations) Rename(ctx context.Context, oldParent *fs.Inode, oldName string, newParent *fs.Inode, newName string, replacement bool) error {
+	return rename(ctx, oldParent, oldName, newParent, newName, replacement)
 }
 
 // GetFile implements fs.InodeOperations.GetFile.
diff --git a/pkg/sentry/fs/tmpfs/tmpfs.go b/pkg/sentry/fs/tmpfs/tmpfs.go
index 1a9d12c0b..a1672a4d0 100644
--- a/pkg/sentry/fs/tmpfs/tmpfs.go
+++ b/pkg/sentry/fs/tmpfs/tmpfs.go
@@ -38,7 +38,7 @@ var fsInfo = fs.Info{
 }
 
 // rename implements fs.InodeOperations.Rename for tmpfs nodes.
-func rename(ctx context.Context, oldParent *fs.Inode, oldName string, newParent *fs.Inode, newName string) error {
+func rename(ctx context.Context, oldParent *fs.Inode, oldName string, newParent *fs.Inode, newName string, replacement bool) error {
 	op, ok := oldParent.InodeOperations.(*Dir)
 	if !ok {
 		return syserror.EXDEV
@@ -47,7 +47,7 @@ func rename(ctx context.Context, oldParent *fs.Inode, oldName string, newParent
 	if !ok {
 		return syserror.EXDEV
 	}
-	return ramfs.Rename(ctx, op.ramfsDir, oldName, np.ramfsDir, newName)
+	return ramfs.Rename(ctx, op.ramfsDir, oldName, np.ramfsDir, newName, replacement)
 }
 
 // Dir is a directory.
@@ -238,8 +238,8 @@ func (d *Dir) newCreateOps() *ramfs.CreateOps {
 }
 
 // Rename implements fs.InodeOperations.Rename.
-func (d *Dir) Rename(ctx context.Context, oldParent *fs.Inode, oldName string, newParent *fs.Inode, newName string) error {
-	return rename(ctx, oldParent, oldName, newParent, newName)
+func (d *Dir) Rename(ctx context.Context, oldParent *fs.Inode, oldName string, newParent *fs.Inode, newName string, replacement bool) error {
+	return rename(ctx, oldParent, oldName, newParent, newName, replacement)
 }
 
 // StatFS implments fs.InodeOperations.StatFS.
@@ -266,8 +266,8 @@ func NewSymlink(ctx context.Context, target string, owner fs.FileOwner, msrc *fs
 }
 
 // Rename implements fs.InodeOperations.Rename.
-func (s *Symlink) Rename(ctx context.Context, oldParent *fs.Inode, oldName string, newParent *fs.Inode, newName string) error {
-	return rename(ctx, oldParent, oldName, newParent, newName)
+func (s *Symlink) Rename(ctx context.Context, oldParent *fs.Inode, oldName string, newParent *fs.Inode, newName string, replacement bool) error {
+	return rename(ctx, oldParent, oldName, newParent, newName, replacement)
 }
 
 // StatFS returns the tmpfs info.
@@ -295,8 +295,8 @@ func NewSocket(ctx context.Context, socket transport.BoundEndpoint, owner fs.Fil
 }
 
 // Rename implements fs.InodeOperations.Rename.
-func (s *Socket) Rename(ctx context.Context, oldParent *fs.Inode, oldName string, newParent *fs.Inode, newName string) error {
-	return rename(ctx, oldParent, oldName, newParent, newName)
+func (s *Socket) Rename(ctx context.Context, oldParent *fs.Inode, oldName string, newParent *fs.Inode, newName string, replacement bool) error {
+	return rename(ctx, oldParent, oldName, newParent, newName, replacement)
 }
 
 // StatFS returns the tmpfs info.
@@ -332,8 +332,8 @@ func NewFifo(ctx context.Context, owner fs.FileOwner, perms fs.FilePermissions,
 }
 
 // Rename implements fs.InodeOperations.Rename.
-func (f *Fifo) Rename(ctx context.Context, oldParent *fs.Inode, oldName string, newParent *fs.Inode, newName string) error {
-	return rename(ctx, oldParent, oldName, newParent, newName)
+func (f *Fifo) Rename(ctx context.Context, oldParent *fs.Inode, oldName string, newParent *fs.Inode, newName string, replacement bool) error {
+	return rename(ctx, oldParent, oldName, newParent, newName, replacement)
 }
 
 // StatFS returns the tmpfs info.