[jdk11u-dev] RFR: 8315135: Memory leak in the native implementation of Pack200.Unpacker.unpack()

[Christoph Langer]

On Mon, 28 Aug 2023 19:17:36 GMT, Volker Simonis <simonis at openjdk.org> wrote:

> This issue was found by Yakov Shafranovich (yakovsh at amazon.com) who also provided the reproducer and proposed a fix.
> 
> The native implementation of the `Pack200.Unpacker` class included in OpenJDK 8 and 11 has a native and heap memory leak that gets triggered when corrupted files are processed. If the native `NativeUnpack::start()` method throws an exception (because of a corrupted input file) its caller `NativeUnpack::run()` fails to call the native `NativeUnpack::finish()` method which is responsible for freeing the allocated native memory and releasing the created global JNI handles. A Java application processing large number of malformed Pack200 files will eventually run either out of native memory or out of heap space and exit with an `OutOfMemoryError`.
> 
> The problem can be demonstrated with the following short test program which will exit with an `OutOfMemoryError` quite quickly if run with `java -Xmx32m NativePack200POC`:
> 
> 
> import java.io.*;
> import java.util.jar.*;
> 
> @SuppressWarnings("removal")
> public class NativePack200POC {
>   public static void main(String[] args) {
>     try {
>       ByteArrayInputStream in = new ByteArrayInputStream("foobar".getBytes());
>       for(int i=0; i < 1_000_000; i++) {
>         try {
>           JarOutputStream out = new JarOutputStream(new ByteArrayOutputStream());
>           Pack200.Unpacker unpacker = Pack200.newUnpacker();
>           unpacker.unpack(in, out);
>         } catch (IOException e) {
>         }
>       }
>     } catch (OutOfMemoryError e) {
>       System.out.println(e);
>       throw e;
>     }
>   }
> }
> 
> 
> The problem can be worked around by disabling the native Pack200 implementation with `-Dcom.sun.java.util.jar.pack.disable.native=true` but the default setting is `-Dcom.sun.java.util.jar.pack.disable.native=false`.
> 
> Notice that this bug can not be fixed in HEAD because the Pack200 functionality has been removed in JDK 14 (https://openjdk.org/jeps/367). I therefore propose to fix this in jdk11u-dev first and then downport the fix to jdk8u-dev as well.
> 

Looks good overall.

The test doesn't use the formatting conventions of OpenJDK Java code, though. Indentation should be 4 spaces and also a space between `if` and the following `(` is missing. Please clean this up before integrating.

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PR Review: https://git.openjdk.org/jdk11u-dev/pull/2100#pullrequestreview-1599712162