From f82d92777207ae3bc6b181a5553a6033acc825b3 Mon Sep 17 00:00:00 2001
From: Jamie Liu <jamieliu@google.com>
Date: Tue, 12 Mar 2024 15:46:40 -0700
Subject: [PATCH] Ensure that files created after save are visible after
 restore.

PiperOrigin-RevId: 615197421
---
 pkg/sentry/fsimpl/gofer/gofer.go        | 16 +++++++++-------
 pkg/sentry/fsimpl/gofer/save_restore.go | 15 ++++++++++-----
 2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/pkg/sentry/fsimpl/gofer/gofer.go b/pkg/sentry/fsimpl/gofer/gofer.go
index d88f8dd2e..103daabc3 100644
--- a/pkg/sentry/fsimpl/gofer/gofer.go
+++ b/pkg/sentry/fsimpl/gofer/gofer.go
@@ -833,15 +833,17 @@ type dentry struct {
 	children map[string]*dentry
 
 	// If this dentry represents a directory, negativeChildrenCache cache
-	// names of negative children.
+	// names of negative children. negativeChildrenCache is not saved since
+	// dentry.prepareSaveRecursive() drops all negative children.
 	//
 	// +checklocks:childrenMu
-	negativeChildrenCache stringFixedCache
-	// If this dentry represents a directory, negativeChildren is the number
-	// of negative children cached in dentry.children
+	negativeChildrenCache stringFixedCache `state:"nosave"`
+	// If this dentry represents a directory, negativeChildren is the number of
+	// negative children cached in dentry.children. negativeChildren is not
+	// saved since dentry.prepareSaveRecursive() drops all negative children.
 	//
 	// +checklocks:childrenMu
-	negativeChildren int
+	negativeChildren int `state:"nosave"`
 
 	// If this dentry represents a directory, syntheticChildren is the number
 	// of child dentries for which dentry.isSynthetic() == true.
@@ -857,9 +859,9 @@ type dentry struct {
 	// childrenSet share the same lifecycle.
 	//
 	// +checklocks:childrenMu
-	dirents []vfs.Dirent
+	dirents []vfs.Dirent `state:"nosave"`
 	// +checklocks:childrenMu
-	childrenSet map[string]struct{}
+	childrenSet map[string]struct{} `state:"nosave"`
 
 	// Cached metadata; protected by metadataMu.
 	// To access:
diff --git a/pkg/sentry/fsimpl/gofer/save_restore.go b/pkg/sentry/fsimpl/gofer/save_restore.go
index 742dcbfd3..9e8decba8 100644
--- a/pkg/sentry/fsimpl/gofer/save_restore.go
+++ b/pkg/sentry/fsimpl/gofer/save_restore.go
@@ -111,11 +111,16 @@ func (d *dentry) prepareSaveRecursive(ctx context.Context) error {
 	}
 	d.childrenMu.Lock()
 	defer d.childrenMu.Unlock()
-	for _, child := range d.children {
-		if child != nil {
-			if err := child.prepareSaveRecursive(ctx); err != nil {
-				return err
-			}
+	for childName, child := range d.children {
+		if child == nil {
+			// Unsaved filesystem state may change across save/restore. Remove
+			// negative entries from d.children to ensure that files created
+			// after save are visible after restore.
+			delete(d.children, childName)
+			continue
+		}
+		if err := child.prepareSaveRecursive(ctx); err != nil {
+			return err
 		}
 	}
 	return nil