RFR (S): 8202650: Enforce group for attach listener file

[Chris Plummer]

Hi Christoph,

It looks like for bsd this code was added to fix JDK-7152800. In that CR 
I see the following:

"The attach framework will verify that the file has the same effective 
owner and group as the currently running process. This will be true on 
linux, since files are created with the effective user and group as 
owner. This will NOT be true always on macos, since the file can have a 
different group if the temporary directory has a different group than 
what we are currently running as."

So it looks like the fix is not necessary for Linux. It wouldn't hurt to 
experiment by setting the s-bit on the directory and see if you have the 
same problem as macos and AIX.

thanks,

Chris

On 5/4/18 7:29 AM, Langer, Christoph wrote:
>
> Hi,
>
> please review a change for correctly setting the group for the attach 
> listener file:
>
> Webrev: http://cr.openjdk.java.net/~clanger/webrevs/8202650.0/ 
> <http://cr.openjdk.java.net/%7Eclanger/webrevs/8202650.0/>
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8202650 
> <https://bugs.openjdk.java.net/browse/JDK-8202650>
>
> The attach listener file, usually /tmp/.java_pid<pid> is created from 
> the hotspot JVM process. Usually it will belong to the process user 
> and group. However, when the directory where it is created has set the 
> s-bit for groups, the group of the directory is taken. This will cause 
> errors when the attach client tries to connect and it is checked 
> whether the group of the attach file matches the client processes' group.
>
> In my webrev I only implemented the change for AIX because we have run 
> into an issue on that platform. But I can see this code already in 
> place for attachListener_bsd.cpp. And I’m wondering if this should 
> also be added to attachListener_linux.cpp because the sticky-bit could 
> be set with the same effects on Linux, too. Any opinions about that?
>
> Thanks and best regards
>
> Christoph
>