8305664: [BACKOUT] (fs) Remove FileSystem support for resolving against a default directory (chdir configuration)

Reviewed-by: alanb

src/java.base/unix/classes/sun/nio/fs/UnixFileSystem.java

@@ -52,7 +52,6 @@ import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.regex.Pattern;
 import jdk.internal.misc.Blocker;
-import jdk.internal.util.StaticProperty;
 import sun.nio.ch.DirectBuffer;
 import sun.nio.ch.IOStatus;
 import sun.security.action.GetPropertyAction;
@@ -74,17 +73,39 @@ abstract class UnixFileSystem
 
     private final UnixFileSystemProvider provider;
     private final byte[] defaultDirectory;
+    private final boolean needToResolveAgainstDefaultDirectory;
     private final UnixPath rootDirectory;
 
     // package-private
-    UnixFileSystem(UnixFileSystemProvider provider) {
-        String dir = StaticProperty.userDir();
+    UnixFileSystem(UnixFileSystemProvider provider, String dir) {
         this.provider = provider;
         this.defaultDirectory = Util.toBytes(UnixPath.normalizeAndCheck(dir));
         if (this.defaultDirectory[0] != '/') {
             throw new RuntimeException("default directory must be absolute");
         }
 
+        // if process-wide chdir is allowed or default directory is not the
+        // process working directory then paths must be resolved against the
+        // default directory.
+        String propValue = GetPropertyAction
+                .privilegedGetProperty("sun.nio.fs.chdirAllowed", "false");
+        boolean chdirAllowed = propValue.isEmpty() ? true : Boolean.parseBoolean(propValue);
+        if (chdirAllowed) {
+            this.needToResolveAgainstDefaultDirectory = true;
+        } else {
+            byte[] cwd = UnixNativeDispatcher.getcwd();
+            boolean defaultIsCwd = (cwd.length == defaultDirectory.length);
+            if (defaultIsCwd) {
+                for (int i=0; i<cwd.length; i++) {
+                    if (cwd[i] != defaultDirectory[i]) {
+                        defaultIsCwd = false;
+                        break;
+                    }
+                }
+            }
+            this.needToResolveAgainstDefaultDirectory = !defaultIsCwd;
+        }
+
         // the root directory
         this.rootDirectory = new UnixPath(this, "/");
     }
@@ -94,6 +115,10 @@ abstract class UnixFileSystem
         return defaultDirectory;
     }
 
+    boolean needToResolveAgainstDefaultDirectory() {
+        return needToResolveAgainstDefaultDirectory;
+    }
+
     boolean isCaseInsensitiveAndPreserving() {
         return false;
     }

src/java.base/unix/classes/sun/nio/fs/UnixFileSystemProvider.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2008, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -75,7 +75,7 @@ public abstract class UnixFileSystemProvider
     private final UnixFileSystem theFileSystem;
 
     public UnixFileSystemProvider() {
-        theFileSystem = newFileSystem();
+        theFileSystem = newFileSystem(StaticProperty.userDir());
     }
 
     UnixFileSystem theFileSystem() {
@@ -83,9 +83,9 @@ public abstract class UnixFileSystemProvider
     }
 
     /**
-     * Constructs a new file system.
+     * Constructs a new file system using the given default directory.
      */
-    abstract UnixFileSystem newFileSystem();
+    abstract UnixFileSystem newFileSystem(String dir);
 
     @Override
     public final String getScheme() {

src/java.base/unix/classes/sun/nio/fs/UnixNativeDispatcher.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2008, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -52,6 +52,11 @@ class UnixNativeDispatcher {
         return buffer;
     }
 
+    /**
+     * char *getcwd(char *buf, size_t size);
+     */
+    static native byte[] getcwd();
+
     /**
      * int dup(int filedes)
      */

src/java.base/unix/classes/sun/nio/fs/UnixPath.java

@@ -138,12 +138,18 @@ class UnixPath implements Path {
 
     // use this path when making system/library calls
     byte[] getByteArrayForSysCalls() {
-        if (!isEmpty()) {
-            return path;
+        // resolve against default directory if required (chdir allowed or
+        // file system default directory is not working directory)
+        if (getFileSystem().needToResolveAgainstDefaultDirectory()) {
+            return resolve(getFileSystem().defaultDirectory(), path);
         } else {
-            // empty path case will access current directory
-            byte[] here = { '.' };
-            return here;
+            if (!isEmpty()) {
+                return path;
+            } else {
+                // empty path case will access current directory
+                byte[] here = { '.' };
+                return here;
+            }
         }
     }
 
@@ -154,7 +160,11 @@ class UnixPath implements Path {
 
     // use this path for permission checks
     String getPathForPermissionCheck() {
-        return toString();
+        if (getFileSystem().needToResolveAgainstDefaultDirectory()) {
+            return Util.toString(getByteArrayForSysCalls());
+        } else {
+            return toString();
+        }
     }
 
     // Checks that the given file is a UnixPath