xen: add error handling for xenbus_printf

[ Upstream commit 84c029a73327cef571eaa61c7d6e67e8031b52ec ]

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@gmail.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index 9122ba2..7abaaa5 100644 (file)
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -291,8 +291,15 @@ static void sysrq_handler(struct xenbus_watch *watch, const char **vec,
                return;
        }
 
-       if (sysrq_key != '\0')
-               xenbus_printf(xbt, "control", "sysrq", "%c", '\0');
+       if (sysrq_key != '\0') {
+               err = xenbus_printf(xbt, "control", "sysrq", "%c", '\0');
+               if (err) {
+                       pr_err("%s: Error %d writing sysrq in control/sysrq\n",
+                              __func__, err);
+                       xenbus_transaction_end(xbt, 1);
+                       return;
+               }
+       }
 
        err = xenbus_transaction_end(xbt, 0);
        if (err == -EAGAIN)
@@ -344,7 +351,12 @@ static int setup_shutdown_watcher(void)
                        continue;
                snprintf(node, FEATURE_PATH_SIZE, "feature-%s",
                         shutdown_handlers[idx].command);
-               xenbus_printf(XBT_NIL, "control", node, "%u", 1);
+               err = xenbus_printf(XBT_NIL, "control", node, "%u", 1);
+               if (err) {
+                       pr_err("%s: Error %d writing %s\n", __func__,
+                               err, node);
+                       return err;
+               }
        }
 
        return 0;