RFR: 8342449: reimplement: JDK-8327114 Attach in Linux may have wrong behavior when pid == ns_pid [v3]

[Laurence Cable]

On 11/12/24 3:33 PM, Serguei Spitsyn wrote:
> On Thu, 7 Nov 2024 04:48:28 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:
>
>>> Larry Cable has updated the pull request incrementally with one additional commit since the last revision:
>>>
>>>    JDK-8342449: fixed missing param in throws msg and renamed local var
>> src/jdk.attach/linux/classes/sun/tools/attach/VirtualMachineImpl.java line 268:
>>
>>> 266:          * however we can also check the target pid's signal masks to see if it catches SIGQUIT and only do so if in
>>> 267:          * fact it does ... this reduces the risk of killing an innocent process in the current ns as opposed to
>>> 268:          * attaching to the actual target JVM ... c.f: checkCatchesAndSendQuitTo() below.
>> This still looks pretty risky and dangerous. I'm thinking if it'd make sense to check that the target process is a VM process. At least, we know how VM processes can use the signal mask. Another concern is that the target VM process might be not exactly the same VM the client was expecting to attach. I don't know what can be done to ensure this correctness.
> It should be okay to file a bug/rfe on this.

it is not feasible to introspect on the target process to determine if 
it is a JVM or not, this is the best case not to send SIGQUIT to a 
process that is neither catching nor blocking it, where the default is 
to terminate it!
>
> -------------
>
> PR Review Comment: https://git.openjdk.org/jdk/pull/21688#discussion_r1838967163