[PATCH 4.9 021/130] xen: add error handling for xenbus_printf

Greg Kroah-Hartman
2018-08-23T08:07:41Z

From: Zhouyang Jia <jiazhouyang09@gmail.com>

[ 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>
---
drivers/xen/manage.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)

--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -291,8 +291,15 @@ static void sysrq_handler(struct xenbus_
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;