Bluetooth: vhci: Fix race at creating hci device

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.

Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 17 insertions, 6 deletions

diff --git a/drivers/bluetooth/hci_vhci.c b/drivers/bluetooth/hci_vhci.c
index f67ea1c090cb..aba31210c802 100644
--- 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;
 };
 
@@ -87,12 +88,15 @@ 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 opcode)
+static int __vhci_create_device(struct vhci_data *data, __u8 opcode)
 {
         struct hci_dev *hdev;
         struct sk_buff *skb;
         __u8 dev_type;
 
+        if (data->hdev)
+                return -EBADFD;
+
         /* bits 0-1 are dev_type (BR/EDR or AMP) */
         dev_type = opcode & 0x03;
 
@@ -151,6 +155,17 @@ static int vhci_create_device(struct vhci_data *data, __u8 opcode)
         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,
                                     struct iov_iter *from)
 {
@@ -191,11 +206,6 @@ 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;
-                }
-
                 opcode = *((__u8 *) skb->data);
                 skb_pull(skb, 1);
 
@@ -320,6 +330,7 @@ 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;