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From:   Zheng Hacker <hackerzheng666@gmail.com>
Date:   Mon, 13 Feb 2023 11:02:14 +0800
Message-ID: <CAJedcCxXpNOk9bxMziaYAzKBWb1RCVJoJn_2y=8WMn6S3vAkCw@mail.gmail.com>
Subject: Re: [PATCH] Bluetooth: hci_core: Fix poential Use-after-Free bug in hci_remove_adv_monitor
To:     Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc:     Zheng Wang <zyytlz.wz@163.com>, marcel@holtmann.org,
        alex000young@gmail.com, johan.hedberg@gmail.com,
        davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
        pabeni@redhat.com, linux-bluetooth@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
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Luiz Augusto von Dentz <luiz.dentz@gmail.com> =E4=BA=8E2023=E5=B9=B42=E6=9C=
=8811=E6=97=A5=E5=91=A8=E5=85=AD 03:53=E5=86=99=E9=81=93=EF=BC=9A
>
> Hi Zheng,
>
> On Thu, Feb 9, 2023 at 8:11 PM Zheng Wang <zyytlz.wz@163.com> wrote:
> >
> > In hci_remove_adv_monitor, if it gets into HCI_ADV_MONITOR_EXT_MSFT cas=
e,
> > the function will free the monitor and print its handle after that.
> >
> > Fix it by switch the order.
> >
> > Fixes: 7cf5c2978f23 ("Bluetooth: hci_sync: Refactor remove Adv Monitor"=
)
> > Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> > ---
> >  net/bluetooth/hci_core.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> > index b65c3aabcd53..db3352c60de6 100644
> > --- a/net/bluetooth/hci_core.c
> > +++ b/net/bluetooth/hci_core.c
> > @@ -1980,9 +1980,9 @@ static int hci_remove_adv_monitor(struct hci_dev =
*hdev,
> >                 goto free_monitor;
> >
> >         case HCI_ADV_MONITOR_EXT_MSFT:
> > -               status =3D msft_remove_monitor(hdev, monitor);
> >                 bt_dev_dbg(hdev, "%s remove monitor %d msft status %d",
> >                            hdev->name, monitor->handle, status);
> > +               status =3D msft_remove_monitor(hdev, monitor);
>
> I wonder if it is not a good idea to move the logging inside
> msft_remove_monitor?
>
> >                 break;
> >         }
> >
Hello Luiz,

Thanks for your quick reply. I think moving it inside msft_remove_monitor
is a good idea. Because the variable status is returned by msft_remove_moni=
tor.
The call chain is
msft_remove_monitor
  ->msft_remove_monitor_sync
    ->msft_le_cancel_monitor_advertisement_cb
      ->hci_free_adv_monitor
        ->kfree(monitor);
We could mov the bt_dev_dbg to the location before
hci_free_adv_monitor calling and delete the releated code in
hci_remove_adv_monitor.

If you agree with that, I'll make another patch.

Best regards,
Zheng Wang