linux-kernel - [PATCH v2] scsi: xen-scsifront: add error handling for xenbus

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Message-Id: <1528992514-53963-1-git-send-email-jiazhouyang09@gmail.com>
Date:   Fri, 15 Jun 2018 00:08:34 +0800
From:   Zhouyang Jia <jiazhouyang09@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Zhouyang Jia <jiazhouyang09@...il.com>,
        Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        xen-devel@...ts.xenproject.org, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] scsi: xen-scsifront: add error handling for xenbus_printf

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@...il.com>
---
v1->v2:
- Fix dereferencing before checking
---
 drivers/scsi/xen-scsifront.c | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/drivers/scsi/xen-scsifront.c b/drivers/scsi/xen-scsifront.c
index 36f59a1..a7f6111 100644
--- a/drivers/scsi/xen-scsifront.c
+++ b/drivers/scsi/xen-scsifront.c
@@ -654,10 +654,16 @@ static int scsifront_dev_reset_handler(struct scsi_cmnd *sc)
 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) {
+			dev_err(&info->dev->dev, "writing dev_state_path\n");
+			return err;
+		}
+	}
 
 	return 0;
 }
@@ -665,10 +671,14 @@ static int scsifront_sdev_configure(struct scsi_device *sdev)
 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)
+			dev_err(&info->dev->dev, "writing dev_state_path\n");
+	}
 }
 
 static struct scsi_host_template scsifront_sht = {
@@ -1003,9 +1013,11 @@ static void scsifront_do_lun_hotplug(struct vscsifrnt_info *info, int op)
 
 			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)
+					dev_err(&dev->dev, "writing dev_state_path\n");
 			}
 			break;
 		case VSCSIFRONT_OP_DEL_LUN:
@@ -1019,10 +1031,13 @@ static void scsifront_do_lun_hotplug(struct vscsifrnt_info *info, int op)
 			}
 			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)
+					dev_err(&dev->dev, "writing dev_state_path\n");
+			}
 			break;
 		default:
 			break;
-- 
2.7.4