From b80021afd2395fd40464ebbeac8f4c8034dee06e Mon Sep 17 00:00:00 2001
From: Jamie Liu <jamieliu@google.com>
Date: Fri, 4 Dec 2020 19:05:26 -0800
Subject: Overlay runsc regular file mounts with regular files.

Fixes #4991

PiperOrigin-RevId: 345800333
---
 pkg/sentry/fsimpl/overlay/copy_up.go | 23 +++--------------------
 1 file changed, 3 insertions(+), 20 deletions(-)

(limited to 'pkg/sentry/fsimpl/overlay')

diff --git a/pkg/sentry/fsimpl/overlay/copy_up.go b/pkg/sentry/fsimpl/overlay/copy_up.go
index 469f3a33d..27b00cf6f 100644
--- a/pkg/sentry/fsimpl/overlay/copy_up.go
+++ b/pkg/sentry/fsimpl/overlay/copy_up.go
@@ -16,7 +16,6 @@ package overlay
 
 import (
 	"fmt"
-	"io"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -129,25 +128,9 @@ func (d *dentry) copyUpLocked(ctx context.Context) error {
 			return err
 		}
 		defer newFD.DecRef(ctx)
-		bufIOSeq := usermem.BytesIOSequence(make([]byte, 32*1024)) // arbitrary buffer size
-		for {
-			readN, readErr := oldFD.Read(ctx, bufIOSeq, vfs.ReadOptions{})
-			if readErr != nil && readErr != io.EOF {
-				cleanupUndoCopyUp()
-				return readErr
-			}
-			total := int64(0)
-			for total < readN {
-				writeN, writeErr := newFD.Write(ctx, bufIOSeq.DropFirst64(total), vfs.WriteOptions{})
-				total += writeN
-				if writeErr != nil {
-					cleanupUndoCopyUp()
-					return writeErr
-				}
-			}
-			if readErr == io.EOF {
-				break
-			}
+		if _, err := vfs.CopyRegularFileData(ctx, newFD, oldFD); err != nil {
+			cleanupUndoCopyUp()
+			return err
 		}
 		d.mapsMu.Lock()
 		defer d.mapsMu.Unlock()
-- 
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