Bluetooth: vhci: Fix race at creating hci device

commit c7c999cb18da88a881e10e07f0724ad0bfaff770 upstream.

hci_vhci driver creates a hci device object dynamically upon each
HCI_VENDOR_PKT write.  Although it checks the already created object
and returns an error, it's still racy and may build multiple hci_dev
objects concurrently when parallel writes are performed, as the device
tracks only a single hci_dev object.

This patch introduces a mutex to protect against the concurrent device
creations.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/bluetooth/hci_vhci.c b/drivers/bluetooth/hci_vhci.c
index 877b6c363d058b639e0ef40f7c8a59d4d331f2ea..e26eb6b606e1af9297eaf091bd9ba38e55bb7aea 100644 (file)
--- a/drivers/bluetooth/hci_vhci.c
+++ b/drivers/bluetooth/hci_vhci.c
@@ -50,6 +50,7 @@ struct vhci_data {
        wait_queue_head_t read_wait;
        struct sk_buff_head readq;
 
+       struct mutex open_mutex;
        struct delayed_work open_timeout;
 };
 
@@ -95,11 +96,14 @@ static int vhci_send_frame(struct hci_dev *hdev, struct sk_buff *skb)
        return 0;
 }
 
-static int vhci_create_device(struct vhci_data *data, __u8 dev_type)
+static int __vhci_create_device(struct vhci_data *data, __u8 dev_type)
 {
        struct hci_dev *hdev;
        struct sk_buff *skb;
 
+       if (data->hdev)
+               return -EBADFD;
+
        skb = bt_skb_alloc(4, GFP_KERNEL);
        if (!skb)
                return -ENOMEM;
@@ -140,6 +144,17 @@ static int vhci_create_device(struct vhci_data *data, __u8 dev_type)
        return 0;
 }
 
+static int vhci_create_device(struct vhci_data *data, __u8 opcode)
+{
+       int err;
+
+       mutex_lock(&data->open_mutex);
+       err = __vhci_create_device(data, opcode);
+       mutex_unlock(&data->open_mutex);
+
+       return err;
+}
+
 static inline ssize_t vhci_get_user(struct vhci_data *data,
                                    const struct iovec *iov,
                                    unsigned long count)
@@ -185,11 +200,6 @@ static inline ssize_t vhci_get_user(struct vhci_data *data,
        case HCI_VENDOR_PKT:
                cancel_delayed_work_sync(&data->open_timeout);
 
-               if (data->hdev) {
-                       kfree_skb(skb);
-                       return -EBADFD;
-               }
-
                dev_type = *((__u8 *) skb->data);
                skb_pull(skb, 1);
 
@@ -318,6 +328,7 @@ static int vhci_open(struct inode *inode, struct file *file)
        skb_queue_head_init(&data->readq);
        init_waitqueue_head(&data->read_wait);
 
+       mutex_init(&data->open_mutex);
        INIT_DELAYED_WORK(&data->open_timeout, vhci_open_timeout);
 
        file->private_data = data;