[PATCH 4.14 64/78] nfc: replace improper check device_is_registered() in netlink related functions

Greg Kroah-Hartman
2022-05-10T13:26:07Z

From: Duoming Zhou <duoming@zju.edu.cn>

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>
---
net/nfc/core.c | 29 ++++++++++++++---------------
1 file changed, 14 insertions(+), 15 deletions(-)

--- a/net/nfc/core.c
+++ b/net/nfc/core.c
@@ -50,7 +50,7 @@ int nfc_fw_download(struct nfc_dev *dev,

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,

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,

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 *de

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 *

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

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 *de

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, u

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,

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->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_de
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);
}