[PATCH 4.6 040/100] Bluetooth: vhci: Fix race at creating hci device

Greg Kroah-Hartman
2016-05-30T21:11:25Z

From: Takashi Iwai <tiwai@suse.de>

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/bluetooth/hci_vhci.c | 23 +++++++++++++++++------
1 file changed, 17 insertions(+), 6 deletions(-)

--- 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_de
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 vhc
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(stru
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
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;