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Update comments in findTargetProcessTmpDirectory()

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This commit is contained in:
Yasumasa Suenaga 2026-01-25 19:52:33 +09:00
parent 8f11d43ba2
commit b6dbde9f9f
1 changed files with 17 additions and 14 deletions
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31
src/jdk.attach/linux/classes/sun/tools/attach/VirtualMachineImpl.java
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@ -258,20 +258,22 @@ public class VirtualMachineImpl extends HotSpotVirtualMachine {
final var tmpOnProcPidRoot = PROC.resolve(Long.toString(pid)).resolve(ROOT_TMP);
/* We need to handle at least 4 different cases:
* 1. Caller and target processes share PID namespace and root filesystem (host to host or container to
* container with both /tmp mounted between containers).
* 2. Caller and target processes share PID namespace and root filesystem but the target process has elevated
* privileges (host to host).
* 3. Caller and target processes share PID namespace but NOT root filesystem (container to container).
* 4. Caller and target processes share neither PID namespace nor root filesystem (host to container)
* 1. Caller and target processes share PID namespace and root
* filesystem (host to host or container to container with both /tmp
* mounted between containers).
* 2. Caller and target processes share PID namespace and root
* filesystem but the target process has elevated privileges
* (host to host).
* 3. Caller and target processes share PID namespace but NOT root
* filesystem (container to container).
* 4. Caller and target processes share neither PID namespace nor root
* filesystem (host to container)
*
* if target is elevated, we cant use /proc/<pid>/... so we have to fallback to /tmp, but that may not be shared
* with the target/attachee process, so we should check whether /tmp on both is same. This method would throw
* AttachNotSupportedException if they are different because we cannot make a connection with target VM.
*
* In addition, we can also check the target pid's signal masks to see if it catches SIGQUIT and only do so if in
* fact it does ... this reduces the risk of killing an innocent process in the current ns as opposed to
* attaching to the actual target JVM ... c.f: checkCatchesAndSendQuitTo() below.
* if target is elevated, we cant use /proc/<pid>/... so we have to
* fallback to /tmp, but that may not be shared with the target/attachee
* process, so we should check whether /tmp on both is same. This method
* would throw AttachOperationFailedException if they are different
* because we cannot make a connection with target VM.
*/
try {
@ -303,7 +305,8 @@ public class VirtualMachineImpl extends HotSpotVirtualMachine {
// exception should not happen.
throw new AssertionError("Unexpected exception", e);
} catch (MonitorException e) {
// Other exceptions (happened at MonitoredHost) would be wrapped with AttachOperationFailedException
// Other exceptions (happened at MonitoredHost) would be wrapped
// with AttachOperationFailedException.
throw new AttachOperationFailedException("Unable to find target proces", e);
}
}