[cinder-csi-plugin] Protect OsInstances global map with mutex (#3123)

The OsInstances map is accessed from both CreateOpenStackProvider
(write) and GetOpenStackProvider (read) without synchronization.
Although current usage is single-threaded at startup, this is a
latent data race if the driver is ever accessed concurrently.

Add a sync.Mutex to guard read and write access to the OsInstances
map, preventing potential concurrent map access panics.

Signed-off-by: Walter Boring <waboring@hemna.com>

Author: hemna

pkg/csi/cinder/openstack/openstack.go

@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"net/http"
 	"os"
+	"sync"
 
 	"github.com/gophercloud/gophercloud/v2"
 	"github.com/gophercloud/gophercloud/v2/openstack"
@@ -147,8 +148,9 @@ func GetConfigFromFiles(configFilePaths []string) (Config, error) {
 const defaultMaxVolAttachLimit int64 = 256
 
 var (
-	OsInstances map[string]IOpenStack
-	configFiles = []string{"/etc/cloud.conf"}
+	OsInstances   map[string]IOpenStack
+	osInstancesMu sync.Mutex
+	configFiles   = []string{"/etc/cloud.conf"}
 )
 
 func InitOpenStackProvider(cfgFiles []string, httpEndpoint string) {
@@ -212,29 +214,35 @@ func CreateOpenStackProvider(cloudName string) (IOpenStack, error) {
 	}
 
 	// Init OpenStack
-	OsInstances[cloudName] = &OpenStack{
+	osInstance := &OpenStack{
 		compute:      computeclient,
 		blockstorage: blockstorageclient,
 		bsOpts:       cfg.BlockStorage,
 		epOpts:       epOpts,
 		metadataOpts: cfg.Metadata,
 	}
 
-	return OsInstances[cloudName], nil
+	osInstancesMu.Lock()
+	OsInstances[cloudName] = osInstance
+	osInstancesMu.Unlock()
+
+	return osInstance, nil
 }
 
 // GetOpenStackProvider returns Openstack Instance
 func GetOpenStackProvider(cloudName string) (IOpenStack, error) {
-	OsInstance, OsInstanceDefined := OsInstances[cloudName]
-	if OsInstanceDefined {
-		return OsInstance, nil
+	osInstancesMu.Lock()
+	osInstance, ok := OsInstances[cloudName]
+	osInstancesMu.Unlock()
+	if ok {
+		return osInstance, nil
 	}
-	OsInstance, err := CreateOpenStackProvider(cloudName)
+	osInstance, err := CreateOpenStackProvider(cloudName)
 	if err != nil {
 		return nil, err
 	}
 
-	return OsInstance, nil
+	return osInstance, nil
 }
 
 // GetMetadataOpts returns metadataopts