Re: [PATCH] Bluetooth: Avoid potential use-after-free in hci_error_reset

[Luiz Augusto von Dentz]

Hi,

On Fri, Jan 5, 2024 at 10:36 AM Luiz Augusto von Dentz
<luiz.dentz@xxxxxxxxx> wrote:
>
> Hi Christophe,
>
> On Fri, Jan 5, 2024 at 2:15 AM Christophe JAILLET
> <christophe.jaillet@xxxxxxxxxx> wrote:
> >
> > Le 04/01/2024 à 12:56, Ying Hsu a écrit :
> > > While handling the HCI_EV_HARDWARE_ERROR event, if the underlying
> > > BT controller is not responding, the GPIO reset mechanism would
> > > free the hci_dev and lead to a use-after-free in hci_error_reset.
> > >
> > > Here's the call trace observed on a ChromeOS device with Intel AX201:
> > >     queue_work_on+0x3e/0x6c
> > >     __hci_cmd_sync_sk+0x2ee/0x4c0 [bluetooth <HASH:3b4a6>]
> > >     ? init_wait_entry+0x31/0x31
> > >     __hci_cmd_sync+0x16/0x20 [bluetooth <HASH:3b4a 6>]
> > >     hci_error_reset+0x4f/0xa4 [bluetooth <HASH:3b4a 6>]
> > >     process_one_work+0x1d8/0x33f
> > >     worker_thread+0x21b/0x373
> > >     kthread+0x13a/0x152
> > >     ? pr_cont_work+0x54/0x54
> > >     ? kthread_blkcg+0x31/0x31
> > >      ret_from_fork+0x1f/0x30
> > >
> > > This patch holds the reference count on the hci_dev while processing
> > > a HCI_EV_HARDWARE_ERROR event to avoid potential crash.
> > >
> > > Signed-off-by: Ying Hsu <yinghsu-F7+t8E8rja9g9hUCZPvPmw@xxxxxxxxxxxxxxxx>
> > > ---
> > > Tested this commit on a chromebook with Intel BT controller.
> > >
> > >   net/bluetooth/hci_core.c | 2 ++
> > >   1 file changed, 2 insertions(+)
> > >
> > > diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> > > index 65601aa52e0d..a42417926028 100644
> > > --- a/net/bluetooth/hci_core.c
> > > +++ b/net/bluetooth/hci_core.c
> > > @@ -1049,6 +1049,7 @@ static void hci_error_reset(struct work_struct *work)
> > >   {
> > >       struct hci_dev *hdev = container_of(work, struct hci_dev, error_reset);
> > >
> > > +     hci_dev_hold(hdev);
> > >       BT_DBG("%s", hdev->name);
> > >
> > >       if (hdev->hw_error)
> > > @@ -1060,6 +1061,7 @@ static void hci_error_reset(struct work_struct *work)
> > >               return;
> >
> >                  ^^^^^
> > Should we also call hci_dev_put() if we hit this return?
>
> Yep, I will fix that since Ive already pushed to bluetooth-next.

Here is the proposed change:

-       if (hci_dev_do_close(hdev))
-               return;
+       if (!hci_dev_do_close(hdev))
+               hci_dev_do_open(hdev);

-       hci_dev_do_open(hdev);
+       hci_dev_put(hdev);

> >
> > CJ
> >
> > >
> > >       hci_dev_do_open(hdev);
> > > +     hci_dev_put(hdev);
> > >   }
> > >
> > >   void hci_uuids_clear(struct hci_dev *hdev)
> >
>
>
> --
> Luiz Augusto von Dentz



-- 
Luiz Augusto von Dentz