RFR: JDK-8271858: Handle to jimage file inherited into child processes (posix)

[Alan Bateman]

On Wed, 4 Aug 2021 12:22:24 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> We should not leak the handle to the jimage file (lib/modules) to childs.
> 
> JDK-8194734 did solve this for windows. We should use FD_CLOEXEC on Posix as well.
> 
> Note that this only poses a problem when a child process is spawned off not via `Runtime.exec` but via another route since the spawnhelper closes all file descriptors.
> 
> ---
> test:
> 
> manually verified that lib/modules now has the FD_CLOEXEC flag set.

src/java.base/unix/native/libjimage/osSupport_unix.cpp line 41:

> 39:  */
> 40: jint osSupport::openReadOnly(const char *path) {
> 41:     return ::open(path, O_CLOEXEC);

This is okay but I think it would be useful to know why this one place needs O_CLOEXEC and not others.

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PR: https://git.openjdk.java.net/jdk/pull/4991