kobject: return error code if writing /sys/.../uevent fails

Propagate error code back to userspace if writing the /sys/.../uevent
file fails. Before, the write operation always returned with success,
even if we failed to recognize the input string or if we failed to
generate the uevent itself.

With the error codes properly propagated back to userspace, we are
able to react in userspace accordingly by not assuming and awaiting
a uevent that is not delivered.

Signed-off-by: Peter Rajnoha <prajnoha@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/bus.c

@@ -611,8 +611,10 @@ static void remove_probe_files(struct bus_type *bus)
 static ssize_t uevent_store(struct device_driver *drv, const char *buf,
 			    size_t count)
 {
-	kobject_synth_uevent(&drv->p->kobj, buf, count);
-	return count;
+	int rc;
+
+	rc = kobject_synth_uevent(&drv->p->kobj, buf, count);
+	return rc ? rc : count;
 }
 static DRIVER_ATTR_WO(uevent);
 
@@ -828,8 +830,10 @@ static void klist_devices_put(struct klist_node *n)
 static ssize_t bus_uevent_store(struct bus_type *bus,
 				const char *buf, size_t count)
 {
-	kobject_synth_uevent(&bus->p->subsys.kobj, buf, count);
-	return count;
+	int rc;
+
+	rc = kobject_synth_uevent(&bus->p->subsys.kobj, buf, count);
+	return rc ? rc : count;
 }
 static BUS_ATTR(uevent, S_IWUSR, NULL, bus_uevent_store);
 

drivers/base/core.c

@@ -1073,8 +1073,14 @@ out:
 static ssize_t uevent_store(struct device *dev, struct device_attribute *attr,
 			    const char *buf, size_t count)
 {
-	if (kobject_synth_uevent(&dev->kobj, buf, count))
+	int rc;
+
+	rc = kobject_synth_uevent(&dev->kobj, buf, count);
+
+	if (rc) {
 		dev_err(dev, "uevent: failed to send synthetic uevent\n");
+		return rc;
+	}
 
 	return count;
 }

kernel/module.c

@@ -1207,8 +1207,10 @@ static ssize_t store_uevent(struct module_attribute *mattr,
 			    struct module_kobject *mk,
 			    const char *buffer, size_t count)
 {
-	kobject_synth_uevent(&mk->kobj, buffer, count);
-	return count;
+	int rc;
+
+	rc = kobject_synth_uevent(&mk->kobj, buffer, count);
+	return rc ? rc : count;
 }
 
 struct module_attribute module_uevent =