Re: [Bluez PATCH v1] adapter: Don't remove device if adapter is powered off

[Luiz Augusto von Dentz <luiz.dentz@gmail.com>]

Hi Archie,

On Mon, Jan 4, 2021 at 11:09 AM Luiz Augusto von Dentz
<luiz.dentz@gmail.com> wrote:
>
> Hi Archie,
>
> On Mon, Dec 28, 2020 at 10:34 PM Archie Pusaka <apusaka@google.com> wrote:
> >
> > From: Archie Pusaka <apusaka@chromium.org>
> >
> > If adapter is powered off when a device is being removed, there is a
> > possibility that the kernel couldn't clean the device's information,
> > for example the pairing information. This causes the kernel to
> > disagree with the user space about whether the device is paired.
> >
> > Therefore, to avoid discrepancy we must not proceed to remove the
> > device within the user space as well.
>
> This sounds like we have a bug in the kernel, aren't we calling
> btd_adapter_remove_bonding or is that failing if the adapter is not
> powered? Hmm it does like it:
>
> This command can only be used when the controller is powered.
>
> > Reviewed-by: Daniel Winkler <danielwinkler@google.com>
> > ---
> >
> >  src/adapter.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/src/adapter.c b/src/adapter.c
> > index ec6a6a64c5..a2abc46706 100644
> > --- a/src/adapter.c
> > +++ b/src/adapter.c
> > @@ -1238,6 +1238,14 @@ void btd_adapter_remove_device(struct btd_adapter *adapter,
> >  {
> >         GList *l;
> >
> > +       /* Test if adapter is or will be powered off.
> > +        * This is to prevent removing the device information only on user
> > +        * space, but failing to do so on the kernel.
> > +        */
> > +       if (!(adapter->current_settings & MGMT_SETTING_POWERED) ||
> > +                       (adapter->pending_settings & MGMT_SETTING_POWERED))
> > +               return;
>
> We might need to return an error here so we can reply with an error on
> Adapter.RemoveDevice.

After some investigation it looks like there is already a similar check:

https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/src/adapter.c#n3238

That perhaps needs to updated or perhaps this is the result of the
device being set to temporary which sets a timer to remove the device
and then in the meantime the adapter is powered off? In that case
perhaps we should clean up the devices set as temporary.

> >         adapter->connect_list = g_slist_remove(adapter->connect_list, dev);
> >
> >         adapter->devices = g_slist_remove(adapter->devices, dev);
> > --
> > 2.29.2.729.g45daf8777d-goog
> >
>
>
> --
> Luiz Augusto von Dentz



-- 
Luiz Augusto von Dentz