RFR: 8307990: jspawnhelper must close its writing side of a pipe before reading from it

[Marius Lichtblau]

On Thu, 1 Jun 2023 10:55:26 GMT, Volker Simonis <simonis at openjdk.org> wrote:

>>> > Sorry, but I don't understand this argument. If we do a short read we will work with corrupted ChildStuff and SpawnInfo
>>> > structures. This can in the extreme case execute arbitrary code (e.g. if ChildStuff.argv is not fully read from the parent). You are
>>> > basically saying it is better to work on corrupted data rather than reporting an error.
>>> 
>>> No I am simply pointing out that this has changed more than just the issue with close. And maybe a short-read does indicate data "corruption" and maybe it should be a fatal error. But I don't know exactly how this might manifest so perhaps there are benign short-reads that actually do happen. Regardless it might be better to split this part out and focus on the close issue here.
>> 
>> Given the purpose and implementation of the `readFully` function, I don't see how it can return anything other than an error or the full requested read length.
>
> Thanks @RogerRiggs and @tstuefe for your help and patience with this PR. I've now updated the [Release Note](https://bugs.openjdk.org/browse/JDK-8308297) for this change to also include the error scenario described by @mlichtblau .

Hey @simonis, thank you for taking the time to include our problem in the fix. I appreciate the detailed explanation of your fix!

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PR Comment: https://git.openjdk.org/jdk/pull/13956#issuecomment-1571841021