8306882: (fs) Path.toRealPath(LinkOption.NOFOLLOW_LINKS) fails when "../../" follows a link

Reviewed-by: alanb

Author: Brian Burkhalter

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

@@ -888,8 +888,15 @@ public Path toRealPath(LinkOption... options) throws IOException {
         }
 
         // if not resolving links then eliminate "." and also ".."
-        // where the previous element is not a link.
+        // where the previous element is neither a link nor "..".
+        // if there is a preceding "..", then it might have followed
+        // a link or a link followed by a sequence of two or more "..".
+        // if for example one has the path "link/../../file",
+        // then if a preceding ".." were eliminated, then the result
+        // would be "<root>/link/file" instead of the correct
+        // "<root>/link/../../file".
         UnixPath result = fs.rootDirectory();
+        boolean parentIsDotDot = false;
         for (int i = 0; i < absolute.getNameCount(); i++) {
             UnixPath element = absolute.getName(i);
 
@@ -898,7 +905,7 @@ public Path toRealPath(LinkOption... options) throws IOException {
                 (element.asByteArray()[0] == '.'))
                 continue;
 
-            // cannot eliminate ".." if previous element is a link
+            // cannot eliminate ".." if previous element is a link or ".."
             if ((element.asByteArray().length == 2) &&
                 (element.asByteArray()[0] == '.') &&
                 (element.asByteArray()[1] == '.'))
@@ -909,13 +916,16 @@ public Path toRealPath(LinkOption... options) throws IOException {
                 } catch (UnixException x) {
                     x.rethrowAsIOException(result);
                 }
-                if (!attrs.isSymbolicLink()) {
+                if (!attrs.isSymbolicLink() && !parentIsDotDot) {
                     result = result.getParent();
                     if (result == null) {
                         result = fs.rootDirectory();
                     }
                     continue;
                 }
+                parentIsDotDot = true;
+            } else {
+                parentIsDotDot = false;
             }
             result = result.resolve(element);
         }

test/jdk/ProblemList.txt

@@ -543,13 +543,15 @@ java/net/MulticastSocket/SetOutgoingIf.java                     8308807 aix-ppc6
 
 java/nio/channels/AsynchronousSocketChannel/StressLoopback.java 8211851 aix-ppc64
 
+java/nio/channels/DatagramChannel/AfterDisconnect.java          8308807 aix-ppc64
+
 java/nio/channels/DatagramChannel/ManySourcesAndTargets.java    8264385 macosx-aarch64
 
 java/nio/channels/DatagramChannel/Unref.java                    8233437 generic-all
 
-jdk/nio/zipfs/TestLocOffsetFromZip64EF.java                     8301183 linux-all
+java/nio/file/Path/ToRealPath.java                              8315273 windows-all
 
-java/nio/channels/DatagramChannel/AfterDisconnect.java          8308807 aix-ppc64
+jdk/nio/zipfs/TestLocOffsetFromZip64EF.java                     8301183 linux-all
 
 ############################################################################
 

test/jdk/java/nio/file/Path/ToRealPath.java

@@ -22,7 +22,7 @@
  */
 
 /* @test
- * @bug 8295753
+ * @bug 8295753 8306882
  * @summary Verify correct operation of Path.toRealPath
  * @library .. /test/lib
  * @build ToRealPath jdk.test.lib.Platform
@@ -142,6 +142,52 @@ public void eliminateDotsNoFollow() throws IOException {
                      DIR.toRealPath(NOFOLLOW_LINKS));
     }
 
+    @Test
+    @EnabledIf("supportsLinks")
+    public void noCollapseDots1() throws IOException {
+        Path subPath = DIR.resolve(Path.of("dir", "subdir"));
+        Path sub = Files.createDirectories(subPath);
+        System.out.println("sub: " + sub);
+        Files.createSymbolicLink(LINK, sub);
+        System.out.println("LINK: " + LINK + " -> " + sub);
+        Path p = Path.of("..", "..", FILE.getFileName().toString());
+        System.out.println("p: " + p);
+        Path path = LINK.resolve(p);
+        System.out.println("path:      " + path);
+        System.out.println("no follow: " + path.toRealPath(NOFOLLOW_LINKS));
+        assertEquals(path.toRealPath(NOFOLLOW_LINKS), path);
+
+        Files.delete(sub);
+        Files.delete(sub.getParent());
+        Files.delete(LINK);
+    }
+
+    @Test
+    @EnabledIf("supportsLinks")
+    public void noCollapseDots2() throws IOException {
+        Path subPath = DIR.resolve(Path.of("dir", "subdir"));
+        Path sub = Files.createDirectories(subPath);
+        Path out = Files.createFile(DIR.resolve(Path.of("out.txt")));
+        Path aaa = DIR.resolve(Path.of("aaa"));
+        Files.createSymbolicLink(aaa, sub);
+        System.out.println("aaa: " + aaa + " -> " + sub);
+        Path bbb = DIR.resolve(Path.of("bbb"));
+        Files.createSymbolicLink(bbb, sub);
+        System.out.println("bbb: " + bbb + " -> " + sub);
+        Path p = Path.of("aaa", "..", "..", "bbb", "..", "..", "out.txt");
+        Path path = DIR.resolve(p);
+        System.out.println("path:      " + path);
+        System.out.println("no follow: " + path.toRealPath(NOFOLLOW_LINKS));
+        assertEquals(path.toRealPath(NOFOLLOW_LINKS), path);
+        System.out.println(path.toRealPath());
+
+        Files.delete(sub);
+        Files.delete(sub.getParent());
+        Files.delete(out);
+        Files.delete(aaa);
+        Files.delete(bbb);
+    }
+
     @Test
     @EnabledOnOs(OS.MAC)
     public final void macOSTests() throws IOException {
@@ -180,12 +226,14 @@ public final void macOSTests() throws IOException {
         assertEquals(noFollow.getName(nc - 4), Path.of("theLink"));
         assertEquals(noFollow.getName(nc - 1), Path.of("theTarget"));
 
+        Files.delete(theLink);
         Files.delete(theTarget);
     }
 
     @AfterAll
     public static void cleanup() throws IOException {
-        Files.delete(SUBDIR);
         Files.delete(FILE);
+        Files.delete(SUBDIR);
+        Files.delete(DIR);
     }
 }