[SSHD-1289] Deadlock during session exit

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 2.9.0
• Fix Version/s: 2.9.1
• Assignee: Thomas Wolf
• Reporter: Evgeny Pasynkov
• Created: 11/Aug/22 11:49
• Updated: 12/Aug/22 20:59
• Resolved: 12/Aug/22 20:59

Description

   java.lang.Thread.State: WAITING
	at java.base@11.0.5/jdk.internal.misc.Unsafe.park(Native Method)
		-  waiting on java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync@c50d1b2
	at java.base@11.0.5/java.util.concurrent.locks.LockSupport.park(LockSupport.java:194)
	at java.base@11.0.5/java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:885)
	at java.base@11.0.5/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:917)
	at java.base@11.0.5/java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1240)
	at java.base@11.0.5/java.util.concurrent.locks.ReentrantReadWriteLock$WriteLock.lock(ReentrantReadWriteLock.java:959)
	at org.apache.sshd.common.session.helpers.KeyExchangeMessageHandler.updateState(KeyExchangeMessageHandler.java:139)
	at org.apache.sshd.common.session.helpers.KeyExchangeMessageHandler.shutdown(KeyExchangeMessageHandler.java:186)
	at org.apache.sshd.common.session.helpers.AbstractSession.preClose(AbstractSession.java:967)
	at org.apache.sshd.common.util.closeable.AbstractCloseable.close(AbstractCloseable.java:94)
	at org.apache.sshd.common.session.helpers.AbstractSessionIoHandler.sessionClosed(AbstractSessionIoHandler.java:46)
	at org.apache.sshd.common.io.nio2.Nio2Session.doCloseImmediately(Nio2Session.java:283)
	at org.apache.sshd.common.util.closeable.AbstractCloseable.close(AbstractCloseable.java:95)
	at org.apache.sshd.common.io.nio2.Nio2Session.exceptionCaught(Nio2Session.java:215)
	at org.apache.sshd.common.io.nio2.Nio2Session.writeBuffer(Nio2Session.java:186)
	at org.apache.sshd.common.session.helpers.AbstractSession.doWritePacket(AbstractSession.java:1118)
	-  locked java.lang.Object@3423f353
	at org.apache.sshd.common.session.helpers.KeyExchangeMessageHandler.writeOrEnqueue(KeyExchangeMessageHandler.java:285)
	at org.apache.sshd.common.session.helpers.KeyExchangeMessageHandler.writePacket(KeyExchangeMessageHandler.java:228)
	at org.apache.sshd.common.session.helpers.AbstractSession.writePacket(AbstractSession.java:1039)
	at org.apache.sshd.common.session.Session.writePacket(Session.java:159)
	at org.apache.sshd.common.session.Session.writePacket(Session.java:145)
	at org.apache.sshd.common.channel.AbstractChannel$GracefulChannelCloseable.close(AbstractChannel.java:637)
	at org.apache.sshd.common.util.closeable.SequentialCloseable$1.operationComplete(SequentialCloseable.java:56)
	at org.apache.sshd.common.util.closeable.SequentialCloseable$1.operationComplete(SequentialCloseable.java:45)
	at org.apache.sshd.common.util.closeable.SequentialCloseable.doClose(SequentialCloseable.java:69)
	at org.apache.sshd.common.util.closeable.SimpleCloseable.close(SimpleCloseable.java:63)
	at org.apache.sshd.common.util.closeable.SequentialCloseable$1.operationComplete(SequentialCloseable.java:56)
	at org.apache.sshd.common.util.closeable.SequentialCloseable$1.operationComplete(SequentialCloseable.java:45)
	at org.apache.sshd.common.future.AbstractSshFuture.lambda$notifyListener$2(AbstractSshFuture.java:162)
	at org.apache.sshd.common.future.AbstractSshFuture$$Lambda$352/0x0000000800890040.call(Unknown Source)
	at org.apache.sshd.common.util.threads.ThreadUtils.runAsInternal(ThreadUtils.java:66)
	at org.apache.sshd.common.future.AbstractSshFuture.notifyListener(AbstractSshFuture.java:161)
	at org.apache.sshd.common.future.DefaultSshFuture.addListener(DefaultSshFuture.java:166)
	at org.apache.sshd.common.util.closeable.SequentialCloseable$1.operationComplete(SequentialCloseable.java:57)
	at org.apache.sshd.common.util.closeable.SequentialCloseable$1.operationComplete(SequentialCloseable.java:45)
	at org.apache.sshd.common.util.closeable.SequentialCloseable.doClose(SequentialCloseable.java:69)
	at org.apache.sshd.common.util.closeable.SimpleCloseable.close(SimpleCloseable.java:63)
	at org.apache.sshd.common.util.closeable.AbstractInnerCloseable.doCloseGracefully(AbstractInnerCloseable.java:41)
	at org.apache.sshd.common.util.closeable.AbstractCloseable.close(AbstractCloseable.java:110)
	at org.apache.sshd.server.channel.ChannelSession.closeShell(ChannelSession.java:916)
	at org.apache.sshd.server.channel.ChannelSession.lambda$prepareCommand$0(ChannelSession.java:779)
	at org.apache.sshd.server.channel.ChannelSession$$Lambda$414/0x00000008008fa440.onExit(Unknown Source)

The lock is acquired in "KeyExchangeMessageHandler.writeOrEnqueue" and then tries to re-acquire in "KeyExchangeMessageHandler.updateState"