Internal change.

PiperOrigin-RevId: 334678513

pkg/sentry/fsimpl/verity/filesystem.go

@@ -693,22 +693,24 @@ func (d *dentry) openLocked(ctx context.Context, rp *vfs.ResolvingPath, opts *vf
 		// be called if a verity FD is created successfully.
 		defer merkleWriter.DecRef(ctx)
 
-		parentMerkleWriter, err = rp.VirtualFilesystem().OpenAt(ctx, d.fs.creds, &vfs.PathOperation{
-			Root:  d.parent.lowerMerkleVD,
-			Start: d.parent.lowerMerkleVD,
-		}, &vfs.OpenOptions{
-			Flags: linux.O_WRONLY | linux.O_APPEND,
-		})
-		if err != nil {
-			if err == syserror.ENOENT {
-				parentPath, _ := d.fs.vfsfs.VirtualFilesystem().PathnameWithDeleted(ctx, d.fs.rootDentry.lowerVD, d.parent.lowerVD)
-				return nil, alertIntegrityViolation(err, fmt.Sprintf("Merkle file for %s expected but not found", parentPath))
+		if d.parent != nil {
+			parentMerkleWriter, err = rp.VirtualFilesystem().OpenAt(ctx, d.fs.creds, &vfs.PathOperation{
+				Root:  d.parent.lowerMerkleVD,
+				Start: d.parent.lowerMerkleVD,
+			}, &vfs.OpenOptions{
+				Flags: linux.O_WRONLY | linux.O_APPEND,
+			})
+			if err != nil {
+				if err == syserror.ENOENT {
+					parentPath, _ := d.fs.vfsfs.VirtualFilesystem().PathnameWithDeleted(ctx, d.fs.rootDentry.lowerVD, d.parent.lowerVD)
+					return nil, alertIntegrityViolation(err, fmt.Sprintf("Merkle file for %s expected but not found", parentPath))
+				}
+				return nil, err
 			}
-			return nil, err
+			// parentMerkleWriter is cleaned up if any error occurs. IncRef
+			// will be called if a verity FD is created successfully.
+			defer parentMerkleWriter.DecRef(ctx)
 		}
-		// parentMerkleWriter is cleaned up if any error occurs. IncRef
-		// will be called if a verity FD is created successfully.
-		defer parentMerkleWriter.DecRef(ctx)
 	}
 
 	fd := &fileDescription{

pkg/sentry/fsimpl/verity/verity.go

@@ -568,7 +568,11 @@ func (fd *fileDescription) enableVerity(ctx context.Context, uio usermem.IO, arg
 	verityMu.Lock()
 	defer verityMu.Unlock()
 
-	if fd.lowerFD == nil || fd.merkleReader == nil || fd.merkleWriter == nil || fd.parentMerkleWriter == nil {
+	// In allowRuntimeEnable mode, the underlying fd and read/write fd for
+	// the Merkle tree file should have all been initialized. For any file
+	// or directory other than the root, the parent Merkle tree file should
+	// have also been initialized.
+	if fd.lowerFD == nil || fd.merkleReader == nil || fd.merkleWriter == nil || (fd.parentMerkleWriter == nil && fd.d != fd.d.fs.rootDentry) {
 		return 0, alertIntegrityViolation(syserror.EIO, "Unexpected verity fd: missing expected underlying fds")
 	}
 
@@ -577,26 +581,28 @@ func (fd *fileDescription) enableVerity(ctx context.Context, uio usermem.IO, arg
 		return 0, err
 	}
 
-	stat, err := fd.parentMerkleWriter.Stat(ctx, vfs.StatOptions{})
-	if err != nil {
-		return 0, err
-	}
+	if fd.parentMerkleWriter != nil {
+		stat, err := fd.parentMerkleWriter.Stat(ctx, vfs.StatOptions{})
+		if err != nil {
+			return 0, err
+		}
 
-	// Write the root hash of fd to the parent directory's Merkle tree
-	// file, as it should be part of the parent Merkle tree data.
-	// parentMerkleWriter is open with O_APPEND, so it should write
-	// directly to the end of the file.
-	if _, err = fd.parentMerkleWriter.Write(ctx, usermem.BytesIOSequence(rootHash), vfs.WriteOptions{}); err != nil {
-		return 0, err
-	}
+		// Write the root hash of fd to the parent directory's Merkle
+		// tree file, as it should be part of the parent Merkle tree
+		// data.  parentMerkleWriter is open with O_APPEND, so it
+		// should write directly to the end of the file.
+		if _, err = fd.parentMerkleWriter.Write(ctx, usermem.BytesIOSequence(rootHash), vfs.WriteOptions{}); err != nil {
+			return 0, err
+		}
 
-	// Record the offset of the root hash of fd in parent directory's
-	// Merkle tree file.
-	if err := fd.merkleWriter.SetXattr(ctx, &vfs.SetXattrOptions{
-		Name:  merkleOffsetInParentXattr,
-		Value: strconv.Itoa(int(stat.Size)),
-	}); err != nil {
-		return 0, err
+		// Record the offset of the root hash of fd in parent directory's
+		// Merkle tree file.
+		if err := fd.merkleWriter.SetXattr(ctx, &vfs.SetXattrOptions{
+			Name:  merkleOffsetInParentXattr,
+			Value: strconv.Itoa(int(stat.Size)),
+		}); err != nil {
+			return 0, err
+		}
 	}
 
 	// Record the size of the data being hashed for fd.