RFR: 8334394: Race condition in Class::protectionDomain

[Weijun Wang]

On Mon, 17 Jun 2024 15:08:26 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Make sure `pd` is always the same object when `getProtectionDomain0` is null.
>
> test/jdk/java/lang/Class/ProtectionDomainRace.java line 42:
> 
>> 40:                 try {
>> 41:                     Subject.doAs(null, ac);
>> 42:                 } catch (Throwable t) {
> 
> This can test for the racy NPE, but it cannot detect if there's distinct allPermDomain objects written by races. Should we add another check to defend against that?

Actually it can. This bug originally breaks the `assert` statement at https://github.com/openjdk/jdk/blob/5cea53d372744ddf1bedaae4667415e6525ef82f/src/java.base/share/classes/java/lang/invoke/MethodHandleImpl.java#L1209.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19752#discussion_r1642973826