[PATCH 4.9 022/130] scsi: xen-scsifront: add error handling for xenbus_printf

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Zhouyang Jia <jiazhouyang09@xxxxxxxxx>

[ Upstream commit 93efbd39870474cc536b9caf4a6efeb03b0bc56f ]

When xenbus_printf fails, the lack of error-handling code may
cause unexpected results.

This patch adds error-handling code after calling xenbus_printf.

Signed-off-by: Zhouyang Jia <jiazhouyang09@xxxxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/scsi/xen-scsifront.c |   33 ++++++++++++++++++++++++++-------
 1 file changed, 26 insertions(+), 7 deletions(-)

--- a/drivers/scsi/xen-scsifront.c
+++ b/drivers/scsi/xen-scsifront.c
@@ -676,10 +676,17 @@ static int scsifront_dev_reset_handler(s
 static int scsifront_sdev_configure(struct scsi_device *sdev)
 {
 	struct vscsifrnt_info *info = shost_priv(sdev->host);
+	int err;
 
-	if (info && current == info->curr)
-		xenbus_printf(XBT_NIL, info->dev->nodename,
+	if (info && current == info->curr) {
+		err = xenbus_printf(XBT_NIL, info->dev->nodename,
 			      info->dev_state_path, "%d", XenbusStateConnected);
+		if (err) {
+			xenbus_dev_error(info->dev, err,
+				"%s: writing dev_state_path", __func__);
+			return err;
+		}
+	}
 
 	return 0;
 }
@@ -687,10 +694,15 @@ static int scsifront_sdev_configure(stru
 static void scsifront_sdev_destroy(struct scsi_device *sdev)
 {
 	struct vscsifrnt_info *info = shost_priv(sdev->host);
+	int err;
 
-	if (info && current == info->curr)
-		xenbus_printf(XBT_NIL, info->dev->nodename,
+	if (info && current == info->curr) {
+		err = xenbus_printf(XBT_NIL, info->dev->nodename,
 			      info->dev_state_path, "%d", XenbusStateClosed);
+		if (err)
+			xenbus_dev_error(info->dev, err,
+				"%s: writing dev_state_path", __func__);
+	}
 }
 
 static struct scsi_host_template scsifront_sht = {
@@ -1025,9 +1037,12 @@ static void scsifront_do_lun_hotplug(str
 
 			if (scsi_add_device(info->host, chn, tgt, lun)) {
 				dev_err(&dev->dev, "scsi_add_device\n");
-				xenbus_printf(XBT_NIL, dev->nodename,
+				err = xenbus_printf(XBT_NIL, dev->nodename,
 					      info->dev_state_path,
 					      "%d", XenbusStateClosed);
+				if (err)
+					xenbus_dev_error(dev, err,
+						"%s: writing dev_state_path", __func__);
 			}
 			break;
 		case VSCSIFRONT_OP_DEL_LUN:
@@ -1041,10 +1056,14 @@ static void scsifront_do_lun_hotplug(str
 			}
 			break;
 		case VSCSIFRONT_OP_READD_LUN:
-			if (device_state == XenbusStateConnected)
-				xenbus_printf(XBT_NIL, dev->nodename,
+			if (device_state == XenbusStateConnected) {
+				err = xenbus_printf(XBT_NIL, dev->nodename,
 					      info->dev_state_path,
 					      "%d", XenbusStateConnected);
+				if (err)
+					xenbus_dev_error(dev, err,
+						"%s: writing dev_state_path", __func__);
+			}
 			break;
 		default:
 			break;