nfc: replace improper check device_is_registered() in netlink related functions

commit da5c0f119203ad9728920456a0f52a6d850c01cd upstream.

The device_is_registered() in nfc core is used to check whether
nfc device is registered in netlink related functions such as
nfc_fw_download(), nfc_dev_up() and so on. Although device_is_registered()
is protected by device_lock, there is still a race condition between
device_del() and device_is_registered(). The root cause is that
kobject_del() in device_del() is not protected by device_lock.

   (cleanup task)         |     (netlink task)
                          |
nfc_unregister_device     | nfc_fw_download
 device_del               |  device_lock
  ...                     |   if (!device_is_registered)//(1)
  kobject_del//(2)        |   ...
 ...                      |  device_unlock

The device_is_registered() returns the value of state_in_sysfs and
the state_in_sysfs is set to zero in kobject_del(). If we pass check in
position (1), then set zero in position (2). As a result, the check
in position (1) is useless.

This patch uses bool variable instead of device_is_registered() to judge
whether the nfc device is registered, which is well synchronized.

Fixes: 3e256b8f8dfa ("NFC: add nfc subsystem core")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/nfc/core.c b/net/nfc/core.c
index 32a2dfc08f480b4614fa2d3f01c9905f277920ce..8c38a21fb0c694e9a59809db6eed96d41baf468f 100644 (file)
--- a/net/nfc/core.c
+++ b/net/nfc/core.c
@@ -50,7 +50,7 @@ int nfc_fw_download(struct nfc_dev *dev, const char *firmware_name)
 
        device_lock(&dev->dev);
 
-       if (!device_is_registered(&dev->dev)) {
+       if (dev->shutting_down) {
                rc = -ENODEV;
                goto error;
        }
@@ -106,7 +106,7 @@ int nfc_dev_up(struct nfc_dev *dev)
 
        device_lock(&dev->dev);
 
-       if (!device_is_registered(&dev->dev)) {
+       if (dev->shutting_down) {
                rc = -ENODEV;
                goto error;
        }
@@ -154,7 +154,7 @@ int nfc_dev_down(struct nfc_dev *dev)
 
        device_lock(&dev->dev);
 
-       if (!device_is_registered(&dev->dev)) {
+       if (dev->shutting_down) {
                rc = -ENODEV;
                goto error;
        }
@@ -218,7 +218,7 @@ int nfc_start_poll(struct nfc_dev *dev, u32 im_protocols, u32 tm_protocols)
 
        device_lock(&dev->dev);
 
-       if (!device_is_registered(&dev->dev)) {
+       if (dev->shutting_down) {
                rc = -ENODEV;
                goto error;
        }
@@ -257,7 +257,7 @@ int nfc_stop_poll(struct nfc_dev *dev)
 
        device_lock(&dev->dev);
 
-       if (!device_is_registered(&dev->dev)) {
+       if (dev->shutting_down) {
                rc = -ENODEV;
                goto error;
        }
@@ -302,7 +302,7 @@ int nfc_dep_link_up(struct nfc_dev *dev, int target_index, u8 comm_mode)
 
        device_lock(&dev->dev);
 
-       if (!device_is_registered(&dev->dev)) {
+       if (dev->shutting_down) {
                rc = -ENODEV;
                goto error;
        }
@@ -346,7 +346,7 @@ int nfc_dep_link_down(struct nfc_dev *dev)
 
        device_lock(&dev->dev);
 
-       if (!device_is_registered(&dev->dev)) {
+       if (dev->shutting_down) {
                rc = -ENODEV;
                goto error;
        }
@@ -412,7 +412,7 @@ int nfc_activate_target(struct nfc_dev *dev, u32 target_idx, u32 protocol)
 
        device_lock(&dev->dev);
 
-       if (!device_is_registered(&dev->dev)) {
+       if (dev->shutting_down) {
                rc = -ENODEV;
                goto error;
        }
@@ -458,7 +458,7 @@ int nfc_deactivate_target(struct nfc_dev *dev, u32 target_idx, u8 mode)
 
        device_lock(&dev->dev);
 
-       if (!device_is_registered(&dev->dev)) {
+       if (dev->shutting_down) {
                rc = -ENODEV;
                goto error;
        }
@@ -505,7 +505,7 @@ int nfc_data_exchange(struct nfc_dev *dev, u32 target_idx, struct sk_buff *skb,
 
        device_lock(&dev->dev);
 
-       if (!device_is_registered(&dev->dev)) {
+       if (dev->shutting_down) {
                rc = -ENODEV;
                kfree_skb(skb);
                goto error;
@@ -562,7 +562,7 @@ int nfc_enable_se(struct nfc_dev *dev, u32 se_idx)
 
        device_lock(&dev->dev);
 
-       if (!device_is_registered(&dev->dev)) {
+       if (dev->shutting_down) {
                rc = -ENODEV;
                goto error;
        }
@@ -611,7 +611,7 @@ int nfc_disable_se(struct nfc_dev *dev, u32 se_idx)
 
        device_lock(&dev->dev);
 
-       if (!device_is_registered(&dev->dev)) {
+       if (dev->shutting_down) {
                rc = -ENODEV;
                goto error;
        }
@@ -1142,6 +1142,7 @@ int nfc_register_device(struct nfc_dev *dev)
                        dev->rfkill = NULL;
                }
        }
+       dev->shutting_down = false;
        device_unlock(&dev->dev);
 
        rc = nfc_genl_device_added(dev);
@@ -1174,12 +1175,10 @@ void nfc_unregister_device(struct nfc_dev *dev)
                rfkill_unregister(dev->rfkill);
                rfkill_destroy(dev->rfkill);
        }
+       dev->shutting_down = true;
        device_unlock(&dev->dev);
 
        if (dev->ops->check_presence) {
-               device_lock(&dev->dev);
-               dev->shutting_down = true;
-               device_unlock(&dev->dev);
                del_timer_sync(&dev->check_pres_timer);
                cancel_work_sync(&dev->check_pres_work);
        }