RFR: 8327114: Attach in Linux may have wrong behaviour when pid == ns_pid (Kubernetes debug container) [v7]

[Larry Cable]

On Sun, 29 Sep 2024 06:23:34 GMT, Sebastian Lövdahl <duke at openjdk.org> wrote:

>> 8327114: Attach in Linux may have wrong behaviour when pid == ns_pid (Kubernetes debug container)
>
> Sebastian Lövdahl has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains eight additional commits since the last revision:
> 
>  - Merge remote-tracking branch 'upstream/master' into 8327114-attach-from-container-to-container
>  - Clarify PID 1 check with comment
>  - Adapt code style
>  - Add test for the elevated privileges case
>  - Remove unused `SELF_PID_NS`
>  - Rewrite in line with suggestion from Larry Cable
>  - Reworked attach logic
>  - 8327114: Attach in Linux may have wrong behaviour when pid == ns_pid (Kubernetes debug container)

I believe we need to wrap the readlink() in an AccessController.doPrivileged() block ... something like this:

`
try {
  targetMountNS = AccessController.doPrivileged(
    (PrivilegedExceptionAction<Optional<Path>>) () -> Optional.ofNullable(Files.readSymbolicLink(procPidPath.resolve(NS_MNT)))
  );
} catch (PrivilegedActionException _) {
// ...
}
`

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PR Comment: https://git.openjdk.org/jdk/pull/19055#issuecomment-2386973409