w1: remove race with sysfs file creation

W1 slave sysfs files are created _after_ userspace is notified that the
device has been added to the system.  Fix that race by moving the
creation/remove of the files to the bus notifier that is there for doing
this type of thing.

Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 73 insertions, 38 deletions

diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
index 0459df843c58..3c798db0152c 100644
--- a/drivers/w1/w1.c
+++ b/drivers/w1/w1.c
@@ -587,6 +587,73 @@ end:
         return err;
 }
 
+/*
+ * Handle sysfs file creation and removal here, before userspace is told that
+ * the device is added / removed from the system
+ */
+static int w1_bus_notify(struct notifier_block *nb, unsigned long action,
+                         void *data)
+{
+        struct device *dev = data;
+        struct w1_slave *sl;
+        int err;
+
+        /*
+         * Only care about slave devices at the moment.  Yes, we should use a
+         * separate "type" for this, but for now, look at the release function
+         * to know which type it is...
+         */
+        if (dev->release != w1_slave_release)
+                return 0;
+
+        sl = dev_to_w1_slave(dev);
+
+        switch (action) {
+        case BUS_NOTIFY_ADD_DEVICE:
+                /* Create our sysfs files before userspace is told about it */
+                /* Create "name" entry */
+                err = device_create_file(&sl->dev, &w1_slave_attr_name);
+                if (err < 0) {
+                        dev_err(&sl->dev,
+                                "sysfs file creation for [%s] failed. err=%d\n",
+                                dev_name(&sl->dev), err);
+                        return err;
+                }
+
+                /* Create "id" entry */
+                err = device_create_file(&sl->dev, &w1_slave_attr_id);
+                if (err < 0) {
+                        dev_err(&sl->dev,
+                                "sysfs file creation for [%s] failed. err=%d\n",
+                                dev_name(&sl->dev), err);
+                        return err;
+                }
+
+                /* if the family driver needs to initialize something... */
+                if (sl->family->fops && sl->family->fops->add_slave &&
+                    ((err = sl->family->fops->add_slave(sl)) < 0)) {
+                        dev_err(&sl->dev,
+                                "sysfs file creation for [%s] failed. err=%d\n",
+                                dev_name(&sl->dev), err);
+                        return err;
+                }
+
+                break;
+        case BUS_NOTIFY_DEL_DEVICE:
+                /* Remove our sysfs files */
+                if (sl->family->fops && sl->family->fops->remove_slave)
+                        sl->family->fops->remove_slave(sl);
+                device_remove_file(&sl->dev, &w1_slave_attr_id);
+                device_remove_file(&sl->dev, &w1_slave_attr_name);
+                break;
+        }
+        return 0;
+}
+
+static struct notifier_block w1_bus_nb = {
+        .notifier_call = w1_bus_notify,
+};
+
 static int __w1_attach_slave_device(struct w1_slave *sl)
 {
         int err;
@@ -615,44 +682,13 @@ static int __w1_attach_slave_device(struct w1_slave *sl)
                 return err;
         }
 
-        /* Create "name" entry */
-        err = device_create_file(&sl->dev, &w1_slave_attr_name);
-        if (err < 0) {
-                dev_err(&sl->dev,
-                        "sysfs file creation for [%s] failed. err=%d\n",
-                        dev_name(&sl->dev), err);
-                goto out_unreg;
-        }
-
-        /* Create "id" entry */
-        err = device_create_file(&sl->dev, &w1_slave_attr_id);
-        if (err < 0) {
-                dev_err(&sl->dev,
-                        "sysfs file creation for [%s] failed. err=%d\n",
-                        dev_name(&sl->dev), err);
-                goto out_rem1;
-        }
 
-        /* if the family driver needs to initialize something... */
-        if (sl->family->fops && sl->family->fops->add_slave &&
-            ((err = sl->family->fops->add_slave(sl)) < 0)) {
-                dev_err(&sl->dev,
-                        "sysfs file creation for [%s] failed. err=%d\n",
-                        dev_name(&sl->dev), err);
-                goto out_rem2;
-        }
+        dev_set_uevent_suppress(&sl->dev, false);
+        kobject_uevent(&sl->dev.kobj, KOBJ_ADD);
 
         list_add_tail(&sl->w1_slave_entry, &sl->master->slist);
 
         return 0;
-
-out_rem2:
-        device_remove_file(&sl->dev, &w1_slave_attr_id);
-out_rem1:
-        device_remove_file(&sl->dev, &w1_slave_attr_name);
-out_unreg:
-        device_unregister(&sl->dev);
-        return err;
 }
 
 static int w1_attach_slave_device(struct w1_master *dev, struct w1_reg_num *rn)
@@ -723,16 +759,11 @@ void w1_slave_detach(struct w1_slave *sl)
 
         list_del(&sl->w1_slave_entry);
 
-        if (sl->family->fops && sl->family->fops->remove_slave)
-                sl->family->fops->remove_slave(sl);
-
         memset(&msg, 0, sizeof(msg));
         memcpy(msg.id.id, &sl->reg_num, sizeof(msg.id));
         msg.type = W1_SLAVE_REMOVE;
         w1_netlink_send(sl->master, &msg);
 
-        device_remove_file(&sl->dev, &w1_slave_attr_id);
-        device_remove_file(&sl->dev, &w1_slave_attr_name);
         device_unregister(&sl->dev);
 
         wait_for_completion(&sl->released);
@@ -1017,6 +1048,10 @@ static int __init w1_init(void)
                 goto err_out_exit_init;
         }
 
+        retval = bus_register_notifier(&w1_bus_type, &w1_bus_nb);
+        if (retval)
+                goto err_out_bus_unregister;
+
         retval = driver_register(&w1_master_driver);
         if (retval) {
                 printk(KERN_ERR