RFR: 8264990: WebEngine crashes with segfault when not loaded through system classloader [v2]

[Arun Joseph]

On Fri, 9 Apr 2021 21:10:46 GMT, Matthias Bläsing <github.com+2179736+matthiasblaesing at openjdk.org> wrote:

>> The functions from FileSystemJava are called from different threads the
>> root problem manifests because the JNI FindClass function behaves
>> differently when called from a context that is the ancestor of a java
>> frame compared to when called in isolation.
>> 
>> A segmentation fault is observed when local storage of a webview is
>> accessed. At that time a new native thread is spun up and that sets up
>> the local storage, by calling into the JVM via
>> WTF::FileSystem::makeAllDirectories. At that point GetFileSystemClass is
>> invoked to get a referenc to the java implementation of the FileSystem.
>> As this is is called from a new native thread (no java context
>> available), JNI uses the system classloader to locate the class. This
>> fails if the JavaFX modules are not on the boot module/class path.
>> 
>> Instead on relying on fetching the class reference everytime it is
>> needed, this change fetches it once when the JavaFX library is loaded
>> and stores it in the WTF namespace.
>> 
>> In addition to this it was observed, that there is no attachment to the
>> JVM done when calling into the filesystem. No fault was observed, but
>> the JNI specs indicate, that the JNIEnv interface is only valid when
>> attached.
>
> Matthias Bläsing has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Revert changes to thread attachment introduced in second commit
>   
>   Thread attachment is handled in
>   jfx/modules/javafx.web/src/main/native/Source/WebKitLegacy/Storage/StorageThread.cpp
>   and thus does not need to be modified.

tests/system/src/test/java/test/com/sun/webkit/LocalStorageAccessTest.java line 36:

> 34: /**
> 35:  * @test
> 36:  * @bug 9069811

The changes looks good. The bug id is not modified at this point.

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PR: https://git.openjdk.java.net/jfx/pull/458