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  1. JDK
  2. JDK-8224181

On child process spawn, child may write to random file descriptor instead of the fail pipe

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        While working on JDK-8223777, I spotted (childstuff.c) the following problem:

        In 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.

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                • Assignee:
                  stuefe Thomas Stuefe
                  Reporter:
                  stuefe Thomas Stuefe
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