On Wed, 20 Apr 2016 15:16:57 +0200, Marcel Holtmann wrote: > > Hi Takashi, > > > 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: <[email protected]> > > Signed-off-by: Takashi Iwai <[email protected]> > > --- > > drivers/bluetooth/hci_vhci.c | 22 ++++++++++++++++------ > > 1 file changed, 16 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/bluetooth/hci_vhci.c b/drivers/bluetooth/hci_vhci.c > > index f67ea1c090cb..39230f30f544 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; > > }; > > > > @@ -87,7 +88,7 @@ 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; > > @@ -151,6 +152,19 @@ 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); > > + if (data->hdev) > > + err = -EBADFD; > > + else > > + 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 +205,6 @@ 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; > > - } > > - > > why not just have the mutex around this block and the vhci_create_device in > the timeout. Wouldn't that achieve exactly the same.
It's just a matter of taste :) I prefer avoiding the duplicated codes; instead of open-coding mutex_lock/unlock and data->hdev check in two places, do it in the common helper. If you prefer other way, I'm fine with it. Just let me know. I'll resubmit the patch. > Since when you actually remove this check, then you still can create another > hci_dev by just writing another vendor packet. That is actually something we > want to avoid. No, it won't happen. The removal of data->hdev in the above is merely moving the check into the mutex protection in vhci_create_device(). thanks, Takashi
