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From: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date: Fri, 5 Jan 2024 10:36:39 -0500
Message-ID: <CABBYNZKo7sFQxE6cE=KTH6-DpL2NzpW7Yybdr49dhdih6+8dcg@mail.gmail.com>
Subject: Re: [PATCH] Bluetooth: Avoid potential use-after-free in hci_error_reset
To: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: yinghsu@chromium.org, chromeos-bluetooth-upstreaming@chromium.org, 
	linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org
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Hi Christophe,

On Fri, Jan 5, 2024 at 2:15=E2=80=AFAM Christophe JAILLET
<christophe.jaillet@wanadoo.fr> wrote:
>
> Le 04/01/2024 =C3=A0 12:56, Ying Hsu a =C3=A9crit :
> > 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@public.gmane.or=
g>
> > ---
> > 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 *w=
ork)
> >   {
> >       struct hci_dev *hdev =3D 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 *w=
ork)
> >               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.

>
> CJ
>
> >
> >       hci_dev_do_open(hdev);
> > +     hci_dev_put(hdev);
> >   }
> >
> >   void hci_uuids_clear(struct hci_dev *hdev)
>


--=20
Luiz Augusto von Dentz