MM-21019 - Fix race in (*Environment).SetPluginState() (#13610)

* MM-21019 - Fix race in (*Environment).SetPluginState()

- We change from passing pointers to registeredPlugin to passing
the struct by value.
- We also add a mutex to the supervisor struct to protect
from racy data access.

* move the immutability comment to the godoc of the Active method

* Changing mut to lock

Co-authored-by: mattermod <mattermod@users.noreply.github.com>

plugin/supervisor.go

@@ -9,6 +9,7 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
+	"sync"
 	"time"
 
 	plugin "github.com/hashicorp/go-plugin"
@@ -17,6 +18,7 @@ import (
 )
 
 type supervisor struct {
+	lock        sync.RWMutex
 	client      *plugin.Client
 	hooks       Hooks
 	implemented [TotalHooksId]bool
@@ -99,17 +101,22 @@ func newSupervisor(pluginInfo *model.BundleInfo, parentLogger *mlog.Logger, apiI
 }
 
 func (sup *supervisor) Shutdown() {
+	sup.lock.RLock()
+	defer sup.lock.RUnlock()
 	if sup.client != nil {
 		sup.client.Kill()
 	}
 }
 
 func (sup *supervisor) Hooks() Hooks {
+	sup.lock.RLock()
+	defer sup.lock.RUnlock()
 	return sup.hooks
 }
 
 // PerformHealthCheck checks the plugin through an an RPC ping.
 func (sup *supervisor) PerformHealthCheck() error {
+	// No need for a lock here because Ping is read-locked.
 	if pingErr := sup.Ping(); pingErr != nil {
 		for pingFails := 1; pingFails < HEALTH_CHECK_PING_FAIL_LIMIT; pingFails++ {
 			pingErr = sup.Ping()
@@ -128,8 +135,9 @@ func (sup *supervisor) PerformHealthCheck() error {
 
 // Ping checks that the RPC connection with the plugin is alive and healthy.
 func (sup *supervisor) Ping() error {
+	sup.lock.RLock()
+	defer sup.lock.RUnlock()
 	client, err := sup.client.Client()
-
 	if err != nil {
 		return err
 	}
@@ -138,5 +146,7 @@ func (sup *supervisor) Ping() error {
 }
 
 func (sup *supervisor) Implements(hookId int) bool {
+	sup.lock.RLock()
+	defer sup.lock.RUnlock()
 	return sup.implemented[hookId]
 }