RFR: 8289643: File descriptor leak with ProcessBuilder.startPipeline

[Roger Riggs]

On Fri, 8 Jul 2022 13:27:42 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> The `ProcessBuilder.pipelineStart()` implementation does not close all of the file descriptors it uses to create the pipeline of processes.
>> 
>> The process calling `pipelineStart()` is creating the pipes between the stages.
>> As each process is launched, the file descriptor is inherited by the child process and
>> the child process `dup`s them to the respective stdin/stdout/stderr fd.  
>> These copies of inherited file descriptors are handled correctly.
>> 
>> Between the launching of each Process, the file descriptor for the read-side of the pipe for the output of the previous process is kept open (in the parent process invoking `pipelineStart`).  The file descriptor is correctly passed to the child and is dup'd to the stdin of the next process.
>> 
>> However, the open file descriptor in the parent is not closed after it has been used as the input for the next Process. 
>> The fix is to close the fd after it has been used as the input of the next process.
>> 
>> A new test verifies that after `pipelineStart` is complete, the same file descriptors are open for Unix Pipes as before the test.
>> The test only runs on Linux using the /proc/<pid>/fd filesystem to identify open file descriptors.
>> 
>> The bug fix is in `ProcessBuilder.pipelineStart` and is applicable to all platforms.
>
> test/jdk/java/lang/ProcessBuilder/PipelineLeaksFD.java line 59:
> 
>> 57:  * @requires (os.family == "linux" & !vm.musl)
>> 58:  * @summary file descriptor leak with ProcessBuilder.startPipeline
>> 59:  * @run testng PipelineLeaksFD
> 
> I wonder if this test should be /othervm, just in case there are pipes left over from previous tests that could interfere with the list found in /proc.

Agreed

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PR: https://git.openjdk.org/jdk/pull/9414