Date:   Tue, 14 Mar 2023 16:06:11 +0100
From:   Simon Horman <simon.horman@corigine.com>
To:     Zheng Hacker <hackerzheng666@gmail.com>
Cc:     Zheng Wang <zyytlz.wz@163.com>, marcel@holtmann.org,
        alex000young@gmail.com, johan.hedberg@gmail.com,
        luiz.dentz@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, pmenzel@molgen.mpg.de
Subject: Re: [PATCH v2] Bluetooth: hci_core: Fix poential Use-after-Free bug
 in hci_remove_adv_monitor
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On Mon, Mar 13, 2023 at 05:55:35PM +0800, Zheng Hacker wrote:
> friendly ping
> 
> Zheng Wang <zyytlz.wz@163.com> 于2023年2月17日周五 18:05写道：
> >
> > In hci_remove_adv_monitor, if it gets into HCI_ADV_MONITOR_EXT_MSFT case,
> > the function will free the monitor and print its handle after that.
> > Fix it by removing the logging into msft_le_cancel_monitor_advertisement_cb
> > before calling hci_free_adv_monitor.
> >
> > Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> > ---
> > v2:
> > - move the logging inside msft_remove_monitor suggested by Luiz
> > ---
> >  net/bluetooth/hci_core.c | 2 --
> >  net/bluetooth/msft.c     | 2 ++
> >  2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> > index b65c3aabcd53..69b82c2907ff 100644
> > --- a/net/bluetooth/hci_core.c
> > +++ b/net/bluetooth/hci_core.c
> > @@ -1981,8 +1981,6 @@ static int hci_remove_adv_monitor(struct hci_dev *hdev,
> >
> >         case HCI_ADV_MONITOR_EXT_MSFT:
> >                 status = msft_remove_monitor(hdev, monitor);
> > -               bt_dev_dbg(hdev, "%s remove monitor %d msft status %d",
> > -                          hdev->name, monitor->handle, status);
> >                 break;

I'm probably missing something obvious.
But from my perspective a simpler fix would be to
move the msft_remove_monitor() call to below the bt_dev_dbg() call.

> >         }
> >
> > diff --git a/net/bluetooth/msft.c b/net/bluetooth/msft.c
> > index bee6a4c656be..4b35f0ed1360 100644
> > --- a/net/bluetooth/msft.c
> > +++ b/net/bluetooth/msft.c
> > @@ -286,6 +286,8 @@ static int msft_le_cancel_monitor_advertisement_cb(struct hci_dev *hdev,
> >                  * suspend. It will be re-monitored on resume.
> >                  */
> >                 if (!msft->suspending) {
> > +                       bt_dev_dbg(hdev, "%s remove monitor %d status %d", hdev->name,
> > +                                  monitor->handle, status);
> >                         hci_free_adv_monitor(hdev, monitor);
> >
> >                         /* Clear any monitored devices by this Adv Monitor */
> > --
> > 2.25.1
> >
>