RFR: 8194154 patch for crash at File.getCanonicalPath()

[Alan Bateman]

On 09/02/2018 18:01, Alan Bateman wrote:
> :
>
> I'll study the patch you have but I think we also need to create 
> issues to get us to the point where changing this system property in a 
> running VM doesn't impact running code.
Looking at it again, I think we should change java.io.UnixFileSystem 
(and the Windows equivalent) to cache the value of user.dir to avoid 
difficult to diagnose issues with bad code changing the value of this 
property in a running VM. This should reduce the issue down to cases 
where user.dir is changed on the command line (never supported either of 
course) to a value that is not "/" but has trailing or duplicate slashes.

When reduced down then the alternatives are to change the native 
canonicalize method as you have done or alternatively do it once at 
UnixFileSystem initialization time so that canonicalize does not have to 
deal with this case. The former would require changing the description 
of the function (it currently reads "The input path is assumed to 
contain no duplicate slashes"), the latter avoids any changes to the 
native implementation.

-Alan


diff -r 0937e5f799df src/java.base/unix/classes/java/io/UnixFileSystem.java
--- a/src/java.base/unix/classes/java/io/UnixFileSystem.java    Sat Feb 
10 07:06:16 2018 -0500
+++ b/src/java.base/unix/classes/java/io/UnixFileSystem.java    Mon Feb 
12 10:49:40 2018 +0000
@@ -34,12 +34,14 @@
      private final char slash;
      private final char colon;
      private final String javaHome;
+    private final String userDir;

      public UnixFileSystem() {
          Properties props = GetPropertyAction.privilegedGetProperties();
          slash = props.getProperty("file.separator").charAt(0);
          colon = props.getProperty("path.separator").charAt(0);
          javaHome = props.getProperty("java.home");
+        userDir = props.getProperty("user.dir");
      }


@@ -128,7 +130,11 @@

      public String resolve(File f) {
          if (isAbsolute(f)) return f.getPath();
-        return resolve(System.getProperty("user.dir"), f.getPath());
+        SecurityManager sm = System.getSecurityManager();
+        if (sm != null) {
+            sm.checkPropertyAccess("user.dir");
+        }
+        return resolve(userDir, f.getPath());
      }

      // Caches for canonicalization results to improve startup performance.