From 47dfba76616a69887f0d5a4be6eb82b5dc5d0f52 Mon Sep 17 00:00:00 2001
From: Nicolas Lacasse <nlacasse@google.com>
Date: Thu, 14 May 2020 09:34:21 -0700
Subject: Port memfd_create to vfs2 and finish implementation of file seals.

Closes #2612.

PiperOrigin-RevId: 311548074
---
 pkg/sentry/fsimpl/tmpfs/filesystem.go | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

(limited to 'pkg/sentry/fsimpl/tmpfs/filesystem.go')

diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go
index e0ad82769..80fa7b29d 100644
--- a/pkg/sentry/fsimpl/tmpfs/filesystem.go
+++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go
@@ -772,5 +772,24 @@ func (fs *filesystem) RemovexattrAt(ctx context.Context, rp *vfs.ResolvingPath,
 func (fs *filesystem) PrependPath(ctx context.Context, vfsroot, vd vfs.VirtualDentry, b *fspath.Builder) error {
 	fs.mu.RLock()
 	defer fs.mu.RUnlock()
-	return genericPrependPath(vfsroot, vd.Mount(), vd.Dentry().Impl().(*dentry), b)
+	mnt := vd.Mount()
+	d := vd.Dentry().Impl().(*dentry)
+	for {
+		if mnt == vfsroot.Mount() && &d.vfsd == vfsroot.Dentry() {
+			return vfs.PrependPathAtVFSRootError{}
+		}
+		if &d.vfsd == mnt.Root() {
+			return nil
+		}
+		if d.parent == nil {
+			if d.name != "" {
+				// This must be an anonymous memfd file.
+				b.PrependComponent("/" + d.name)
+				return vfs.PrependPathSyntheticError{}
+			}
+			return vfs.PrependPathAtNonMountRootError{}
+		}
+		b.PrependComponent(d.name)
+		d = d.parent
+	}
 }
-- 
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