RFR(xs): 8224181: On child process spawn, child may write to random file descriptor instead of the fail pipe

[Thomas Stüfe]

Thank you Roger!

On Tue, Jun 4, 2019 at 5:13 PM Roger Riggs <Roger.Riggs at oracle.com> wrote:

> H Thomas,
>
> Looks ok.
>
> Roger
>
>
> On 06/04/2019 09:23 AM, Thomas Stüfe wrote:
> > Hi all,
> >
> > may I please have reviews for this small fix:
> >
> > Bug: https://bugs.openjdk.java.net/browse/JDK-8224181
> > cr:
> >
> http://cr.openjdk.java.net/~stuefe/webrevs/8224181-on-child-process-spawn--child-may-write-to-wrong-file-descriptor-instead-of-the-fail-pipe/webrev.00/webrev/
> >
> > In sub process error handling code (WhyCantJonnyExec) child signals error
> > to parent by writing an error code to the fail pipe. It does that using
> the
> > hard wired fail pipe write-end fd (FAIL_FILENO, usually 4). But that only
> > works as intended after the fail pipe write end has been successfully
> > dup2'ed to FAIL_FILENO.
> >
> > If an error happens before that, error code will still be written to
> > FAIL_FILENO, which may be an invalid file handle - which is almost
> benign -
> > or refer to an unrelated file descriptor the child inherited and did not
> > close yet - which is not good.
> >
> > Cheers, Thomas
>
>