From 485356c3d3d632e270f44c45ec16cd49c97a205a Mon Sep 17 00:00:00 2001
From: Michael Smithhisler <michael.smithhisler@hashicorp.com>
Date: Wed, 27 Aug 2025 15:00:16 -0400
Subject: [PATCH] csi: fix volume registration error (#26642)

---
 .changelog/26642.txt           | 3 +++
 api/csi.go                     | 1 +
 command/agent/csi_endpoint.go  | 2 +-
 command/volume_register_csi.go | 6 ++++--
 nomad/csi_endpoint.go          | 1 +
 nomad/structs/csi.go           | 3 ++-
 6 files changed, 12 insertions(+), 4 deletions(-)
 create mode 100644 .changelog/26642.txt

diff --git a/.changelog/26642.txt b/.changelog/26642.txt
new file mode 100644
index 000000000..630685a75
--- /dev/null
+++ b/.changelog/26642.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+csi: fix EOF error when registering volumes
+```
diff --git a/api/csi.go b/api/csi.go
index 47f48f478..7177edaab 100644
--- a/api/csi.go
+++ b/api/csi.go
@@ -503,6 +503,7 @@ type CSIVolumeRegisterRequest struct {
 type CSIVolumeRegisterResponse struct {
 	Volumes  []*CSIVolume
 	Warnings string
+	QueryMeta
 }
 
 type CSIVolumeDeregisterRequest struct {
diff --git a/command/agent/csi_endpoint.go b/command/agent/csi_endpoint.go
index 325ce5bb6..d45bfa9ca 100644
--- a/command/agent/csi_endpoint.go
+++ b/command/agent/csi_endpoint.go
@@ -146,7 +146,7 @@ func (s *HTTPServer) csiVolumeRegister(resp http.ResponseWriter, req *http.Reque
 
 	setMeta(resp, &out.QueryMeta)
 
-	return nil, nil
+	return out, nil
 }
 
 func (s *HTTPServer) csiVolumeCreate(resp http.ResponseWriter, req *http.Request) (interface{}, error) {
diff --git a/command/volume_register_csi.go b/command/volume_register_csi.go
index aa5e60551..37ce5137f 100644
--- a/command/volume_register_csi.go
+++ b/command/volume_register_csi.go
@@ -35,9 +35,11 @@ func (c *VolumeRegisterCommand) csiRegister(client *api.Client, ast *ast.File, o
 				fmt.Sprintf("[bold][yellow]Volume Warnings:\n%s[reset]\n", resp.Warnings)))
 	}
 
-	vol = resp.Volumes[0] // note: the command only ever returns 1 volume from the API
+	for _, vol := range resp.Volumes {
+		// note: the command only ever returns 1 volume from the API
+		c.Ui.Output(fmt.Sprintf("Volume %q registered", vol.ID))
+	}
 
-	c.Ui.Output(fmt.Sprintf("Volume %q registered", vol.ID))
 	return 0
 }
 
diff --git a/nomad/csi_endpoint.go b/nomad/csi_endpoint.go
index f2c02b79e..4655fc860 100644
--- a/nomad/csi_endpoint.go
+++ b/nomad/csi_endpoint.go
@@ -371,6 +371,7 @@ func (v *CSIVolume) Register(args *structs.CSIVolumeRegisterRequest, reply *stru
 		return err
 	}
 
+	reply.Volumes = args.Volumes
 	reply.Index = index
 	v.srv.setQueryMeta(&reply.QueryMeta)
 	return nil
diff --git a/nomad/structs/csi.go b/nomad/structs/csi.go
index 7aee0a04d..150a09e29 100644
--- a/nomad/structs/csi.go
+++ b/nomad/structs/csi.go
@@ -879,9 +879,10 @@ type CSIVolumeRegisterRequest struct {
 }
 
 type CSIVolumeRegisterResponse struct {
+	Volumes []*CSIVolume
+
 	// Warnings are non-fatal messages from Enterprise policy enforcement
 	Warnings string
-
 	QueryMeta
 }