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; } @@ -1126,6 +1126,7 @@ int nfc_register_device(struct nfc_dev * dev->rfkill = NULL; } } + dev->shutting_down = false; device_unlock(&dev->dev);
rc = nfc_genl_device_added(dev); @@ -1158,12 +1159,10 @@ 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); }