From 989d7d9fcfee20c802e2b4ab848e14bb2a44cb2f Mon Sep 17 00:00:00 2001
From: Tim Gross <tgross@hashicorp.com>
Date: Mon, 12 Dec 2022 08:42:57 -0500
Subject: [PATCH] csi: avoid a nil pointer when handling plugin events (#15518)

If a plugin crashes quickly enough, we can get into a situation where the
deregister function is called before it's ever registered. Safely handle the
resulting nil pointer in the dynamic registry by not emitting a plugin event,
but also update the plugin event handler to tolerate nil pointers in case we
wire it up elsewhere in the future.
---
 .changelog/15518.txt                       |  3 +++
 client/dynamicplugins/registry.go          | 12 +++++++-----
 client/pluginmanager/csimanager/manager.go |  2 +-
 3 files changed, 11 insertions(+), 6 deletions(-)
 create mode 100644 .changelog/15518.txt

diff --git a/.changelog/15518.txt b/.changelog/15518.txt
new file mode 100644
index 000000000..d081950b9
--- /dev/null
+++ b/.changelog/15518.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+csi: Fixed a bug where a crashing plugin could panic the Nomad client
+```
diff --git a/client/dynamicplugins/registry.go b/client/dynamicplugins/registry.go
index 3059c1a27..4515c64fb 100644
--- a/client/dynamicplugins/registry.go
+++ b/client/dynamicplugins/registry.go
@@ -269,12 +269,14 @@ func (d *dynamicRegistry) DeregisterPlugin(ptype, name, allocID string) error {
 		}
 	}
 
-	broadcaster := d.broadcasterForPluginType(ptype)
-	event := &PluginUpdateEvent{
-		EventType: EventTypeDeregistered,
-		Info:      info,
+	if info != nil {
+		broadcaster := d.broadcasterForPluginType(ptype)
+		event := &PluginUpdateEvent{
+			EventType: EventTypeDeregistered,
+			Info:      info,
+		}
+		broadcaster.broadcast(event)
 	}
-	broadcaster.broadcast(event)
 
 	return d.sync()
 }
diff --git a/client/pluginmanager/csimanager/manager.go b/client/pluginmanager/csimanager/manager.go
index a5b2f51cd..178b0fe15 100644
--- a/client/pluginmanager/csimanager/manager.go
+++ b/client/pluginmanager/csimanager/manager.go
@@ -149,7 +149,7 @@ func (c *csiManager) resyncPluginsFromRegistry(ptype string) {
 
 // handlePluginEvent syncs a single event against the plugin registry
 func (c *csiManager) handlePluginEvent(event *dynamicplugins.PluginUpdateEvent) {
-	if event == nil {
+	if event == nil || event.Info == nil {
 		return
 	}
 	c.logger.Trace("dynamic plugin event",