[PATCH 5.4 20/52] nfc: replace improper check device_is_registered() in netlink related functions

Greg Kroah-Hartman
2022-05-10T13:45:01Z

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
@@ -38,7 +38,7 @@ 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;
}
@@ -94,7 +94,7 @@ 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;
}
@@ -142,7 +142,7 @@ 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;
}
@@ -206,7 +206,7 @@ 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;
}
@@ -245,7 +245,7 @@ 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;
}
@@ -290,7 +290,7 @@ 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;
}
@@ -334,7 +334,7 @@ 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;
}
@@ -400,7 +400,7 @@ 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;
}
@@ -446,7 +446,7 @@ 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;
}
@@ -493,7 +493,7 @@ 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;
@@ -550,7 +550,7 @@ 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;
}
@@ -599,7 +599,7 @@ 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;
}
@@ -1127,6 +1127,7 @@ int nfc_register_device(struct nfc_dev *
dev->rfkill = NULL;
}
}
+ dev->shutting_down = false;
device_unlock(&dev->dev);

rc = nfc_genl_device_added(dev);
@@ -1159,12 +1160,10 @@ 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);
}