4 files changed, 53 insertions, 39 deletions
diff --git a/pkg/sentry/fsimpl/kernfs/filesystem.go b/pkg/sentry/fsimpl/kernfs/filesystem.go
index f81056023..e77523f22 100644
--- a/pkg/sentry/fsimpl/kernfs/filesystem.go
+++ b/pkg/sentry/fsimpl/kernfs/filesystem.go
@@ -207,24 +207,23 @@ func (fs *Filesystem) walkParentDirLocked(ctx context.Context, rp *vfs.Resolving
 // Preconditions:
 // * Filesystem.mu must be locked for at least reading.
 // * isDir(parentInode) == true.
-func checkCreateLocked(ctx context.Context, rp *vfs.ResolvingPath, parent *Dentry) (string, error) {
-	if err := parent.inode.CheckPermissions(ctx, rp.Credentials(), vfs.MayWrite|vfs.MayExec); err != nil {
-		return "", err
+func checkCreateLocked(ctx context.Context, creds *auth.Credentials, name string, parent *Dentry) error {
+	if err := parent.inode.CheckPermissions(ctx, creds, vfs.MayWrite|vfs.MayExec); err != nil {
+		return err
 	}
-	pc := rp.Component()
-	if pc == "." || pc == ".." {
-		return "", syserror.EEXIST
+	if name == "." || name == ".." {
+		return syserror.EEXIST
 	}
-	if len(pc) > linux.NAME_MAX {
-		return "", syserror.ENAMETOOLONG
+	if len(name) > linux.NAME_MAX {
+		return syserror.ENAMETOOLONG
 	}
-	if _, ok := parent.children[pc]; ok {
-		return "", syserror.EEXIST
+	if _, ok := parent.children[name]; ok {
+		return syserror.EEXIST
 	}
 	if parent.VFSDentry().IsDead() {
-		return "", syserror.ENOENT
+		return syserror.ENOENT
 	}
-	return pc, nil
+	return nil
 }
 
 // checkDeleteLocked checks that the file represented by vfsd may be deleted.
@@ -265,7 +264,7 @@ func (fs *Filesystem) Release(ctx context.Context) {
 //
 // Precondition: Filesystem.mu is held.
 func (d *Dentry) releaseKeptDentriesLocked(ctx context.Context) {
-	if d.inode.Keep() {
+	if d.inode.Keep() && d != d.fs.root {
 		d.decRefLocked(ctx)
 	}
 
@@ -352,10 +351,13 @@ func (fs *Filesystem) LinkAt(ctx context.Context, rp *vfs.ResolvingPath, vd vfs.
 
 	parent.dirMu.Lock()
 	defer parent.dirMu.Unlock()
-	pc, err := checkCreateLocked(ctx, rp, parent)
-	if err != nil {
+	pc := rp.Component()
+	if err := checkCreateLocked(ctx, rp.Credentials(), pc, parent); err != nil {
 		return err
 	}
+	if rp.MustBeDir() {
+		return syserror.ENOENT
+	}
 	if rp.Mount() != vd.Mount() {
 		return syserror.EXDEV
 	}
@@ -394,8 +396,8 @@ func (fs *Filesystem) MkdirAt(ctx context.Context, rp *vfs.ResolvingPath, opts v
 
 	parent.dirMu.Lock()
 	defer parent.dirMu.Unlock()
-	pc, err := checkCreateLocked(ctx, rp, parent)
-	if err != nil {
+	pc := rp.Component()
+	if err := checkCreateLocked(ctx, rp.Credentials(), pc, parent); err != nil {
 		return err
 	}
 	if err := rp.Mount().CheckBeginWrite(); err != nil {
@@ -430,10 +432,13 @@ func (fs *Filesystem) MknodAt(ctx context.Context, rp *vfs.ResolvingPath, opts v
 
 	parent.dirMu.Lock()
 	defer parent.dirMu.Unlock()
-	pc, err := checkCreateLocked(ctx, rp, parent)
-	if err != nil {
+	pc := rp.Component()
+	if err := checkCreateLocked(ctx, rp.Credentials(), pc, parent); err != nil {
 		return err
 	}
+	if rp.MustBeDir() {
+		return syserror.ENOENT
+	}
 	if err := rp.Mount().CheckBeginWrite(); err != nil {
 		return err
 	}
@@ -657,8 +662,8 @@ func (fs *Filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa
 
 	// Can we create the dst dentry?
 	var dst *Dentry
-	pc, err := checkCreateLocked(ctx, rp, dstDir)
-	switch err {
+	pc := rp.Component()
+	switch err := checkCreateLocked(ctx, rp.Credentials(), pc, dstDir); err {
 	case nil:
 		// Ok, continue with rename as replacement.
 	case syserror.EEXIST:
@@ -822,10 +827,13 @@ func (fs *Filesystem) SymlinkAt(ctx context.Context, rp *vfs.ResolvingPath, targ
 	parent.dirMu.Lock()
 	defer parent.dirMu.Unlock()
 
-	pc, err := checkCreateLocked(ctx, rp, parent)
-	if err != nil {
+	pc := rp.Component()
+	if err := checkCreateLocked(ctx, rp.Credentials(), pc, parent); err != nil {
 		return err
 	}
+	if rp.MustBeDir() {
+		return syserror.ENOENT
+	}
 	if err := rp.Mount().CheckBeginWrite(); err != nil {
 		return err
 	}
diff --git a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
index d9d76758a..eac578f25 100644
--- a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
+++ b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
@@ -568,13 +568,6 @@ func (o *OrderedChildren) RmDir(ctx context.Context, name string, child Inode) e
 	return o.Unlink(ctx, name, child)
 }
 
-// +stateify savable
-type renameAcrossDifferentImplementationsError struct{}
-
-func (renameAcrossDifferentImplementationsError) Error() string {
-	return "rename across inodes with different implementations"
-}
-
 // Rename implements Inode.Rename.
 //
 // Precondition: Rename may only be called across two directory inodes with
@@ -585,13 +578,18 @@ func (renameAcrossDifferentImplementationsError) Error() string {
 //
 // Postcondition: reference on any replaced dentry transferred to caller.
 func (o *OrderedChildren) Rename(ctx context.Context, oldname, newname string, child, dstDir Inode) error {
+	if !o.writable {
+		return syserror.EPERM
+	}
+
 	dst, ok := dstDir.(interface{}).(*OrderedChildren)
 	if !ok {
-		return renameAcrossDifferentImplementationsError{}
+		return syserror.EXDEV
 	}
-	if !o.writable || !dst.writable {
+	if !dst.writable {
 		return syserror.EPERM
 	}
+
 	// Note: There's a potential deadlock below if concurrent calls to Rename
 	// refer to the same src and dst directories in reverse. We avoid any
 	// ordering issues because the caller is required to serialize concurrent
@@ -662,7 +660,7 @@ var _ Inode = (*StaticDirectory)(nil)
 func NewStaticDir(ctx context.Context, creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, perm linux.FileMode, children map[string]Inode, fdOpts GenericDirectoryFDOptions) Inode {
 	inode := &StaticDirectory{}
 	inode.Init(ctx, creds, devMajor, devMinor, ino, perm, fdOpts)
-	inode.EnableLeakCheck()
+	inode.InitRefs()
 
 	inode.OrderedChildren.Init(OrderedChildrenOptions{})
 	links := inode.OrderedChildren.Populate(children)
diff --git a/pkg/sentry/fsimpl/kernfs/kernfs.go b/pkg/sentry/fsimpl/kernfs/kernfs.go
index abb477c7d..c14abcff4 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs.go
@@ -222,7 +222,9 @@ func (d *Dentry) IncRef() {
 	// d.refs may be 0 if d.fs.mu is locked, which serializes against
 	// d.cacheLocked().
 	r := atomic.AddInt64(&d.refs, 1)
-	refsvfs2.LogIncRef(d, r)
+	if d.LogRefs() {
+		refsvfs2.LogIncRef(d, r)
+	}
 }
 
 // TryIncRef implements vfs.DentryImpl.TryIncRef.
@@ -233,7 +235,9 @@ func (d *Dentry) TryIncRef() bool {
 			return false
 		}
 		if atomic.CompareAndSwapInt64(&d.refs, r, r+1) {
-			refsvfs2.LogTryIncRef(d, r+1)
+			if d.LogRefs() {
+				refsvfs2.LogTryIncRef(d, r+1)
+			}
 			return true
 		}
 	}
@@ -242,7 +246,9 @@ func (d *Dentry) TryIncRef() bool {
 // DecRef implements vfs.DentryImpl.DecRef.
 func (d *Dentry) DecRef(ctx context.Context) {
 	r := atomic.AddInt64(&d.refs, -1)
-	refsvfs2.LogDecRef(d, r)
+	if d.LogRefs() {
+		refsvfs2.LogDecRef(d, r)
+	}
 	if r == 0 {
 		d.fs.mu.Lock()
 		d.cacheLocked(ctx)
@@ -254,7 +260,9 @@ func (d *Dentry) DecRef(ctx context.Context) {
 
 func (d *Dentry) decRefLocked(ctx context.Context) {
 	r := atomic.AddInt64(&d.refs, -1)
-	refsvfs2.LogDecRef(d, r)
+	if d.LogRefs() {
+		refsvfs2.LogDecRef(d, r)
+	}
 	if r == 0 {
 		d.cacheLocked(ctx)
 	} else if r < 0 {
diff --git a/pkg/sentry/fsimpl/kernfs/kernfs_test.go b/pkg/sentry/fsimpl/kernfs/kernfs_test.go
index 2418eec44..e63588e33 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs_test.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs_test.go
@@ -109,7 +109,7 @@ func (fs *filesystem) newReadonlyDir(ctx context.Context, creds *auth.Credential
 	dir := &readonlyDir{}
 	dir.attrs.Init(ctx, creds, 0 /* devMajor */, 0 /* devMinor */, fs.NextIno(), linux.ModeDirectory|mode)
 	dir.OrderedChildren.Init(kernfs.OrderedChildrenOptions{})
-	dir.EnableLeakCheck()
+	dir.InitRefs()
 	dir.IncLinks(dir.OrderedChildren.Populate(contents))
 	return dir
 }
@@ -147,7 +147,7 @@ func (fs *filesystem) newDir(ctx context.Context, creds *auth.Credentials, mode
 	dir.fs = fs
 	dir.attrs.Init(ctx, creds, 0 /* devMajor */, 0 /* devMinor */, fs.NextIno(), linux.ModeDirectory|mode)
 	dir.OrderedChildren.Init(kernfs.OrderedChildrenOptions{Writable: true})
-	dir.EnableLeakCheck()
+	dir.InitRefs()
 
 	dir.IncLinks(dir.OrderedChildren.Populate(contents))
 	return dir