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

[Laurence Cable]

On 5/3/24 10:43 AM, jdoylei wrote:
> On Thu, 2 May 2024 10:13:51 GMT, Sebastian Lövdahl <duke at openjdk.org> wrote:
>
>> 8327114: Attach in Linux may have wrong behaviour when pid == ns_pid (Kubernetes debug container)
>> I think it boils down to the same reason as why the fix for JDK-8226919 was needed in the first place - a non-root user cannot read the symlinks in `/proc/<pid>/ns` for a process running with more privileges even though it's run by the same non-root user.
> @slovdahl - In that test case (target JVM process has more privileges), where is the attach file created?  Does jcmd end up writing it to `/tmp`?  Or does `/proc/<pid>/cwd` work?  Just curious whether the elevated-privileges scenario affects the attach file and socket file locations equally.

note that the use of 'cwd' is a historical artifact, while the 
.attach_<pid> file can be written to 'cwd' the actual attach socket file 
.java_<pid> is always written to /tmp
>
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> PR Comment: https://git.openjdk.org/jdk/pull/19055#issuecomment-2093481534