Close the controlFD used to fstat upon an inode cache hit

Fixes #12125

PiperOrigin-RevId: 805463538

Author: tranji-cloud

pkg/sentry/fsimpl/gofer/directfs_inode.go

@@ -134,8 +134,7 @@ func (fs *filesystem) newDirectfsDentry(controlFD int) (*dentry, error) {
 		d dentry
 		i directfsInode
 	}{}
-
-	temp.d.inode = fs.getOrCreateInode(inoKey, func() *inode {
+	temp.d.inode = fs.getOrCreateInode(inoKey, func() { _ = unix.Close(controlFD) }, func() *inode {
 		temp.i = directfsInode{
 			inode: inode{
 				fs:        fs,

pkg/sentry/fsimpl/gofer/gofer.go

@@ -260,14 +260,16 @@ type filesystem struct {
 	released atomicbitops.Int32
 }
 
-// getOrCreateInode returns the inode for the given inoKey and increments its reference count.
-// If the inode is not found, then createInode is called and the new inode is returned.
+// getOrCreateInode returns the inode for the given inoKey and upon inode cache
+// hit, calls onCacheHit and increments the inode's reference count. On cache
+// miss, createInode is called and the new inode is returned.
 // getOrCreateInode locks fs.inodeMu.
 // The caller is responsible for decrementing the inode's reference count when done.
-func (fs *filesystem) getOrCreateInode(inoKey inoKey, createInode func() *inode) *inode {
+func (fs *filesystem) getOrCreateInode(inoKey inoKey, onCacheHit func(), createInode func() *inode) *inode {
 	fs.inodeMu.Lock()
 	defer fs.inodeMu.Unlock()
 	if cachedInode, ok := fs.inodeByKey[inoKey]; ok {
+		onCacheHit()
 		cachedInode.incRef()
 		return cachedInode
 	}

pkg/sentry/fsimpl/gofer/lisafs_inode.go

@@ -125,7 +125,9 @@ func (fs *filesystem) newLisafsDentry(ctx context.Context, ino *lisafs.Inode) (*
 		d dentry
 		i lisafsInode
 	}{}
-	temp.d.inode = fs.getOrCreateInode(inoKey, func() *inode {
+	temp.d.inode = fs.getOrCreateInode(inoKey, func() {
+		fs.client.CloseFD(ctx, ino.ControlFD, false /* flush */)
+	}, func() *inode {
 		temp.i = lisafsInode{
 			inode: inode{
 				fs:        fs,