linux-kernel - Re: [PATCH 1/2] Bluetooth: fix debugfs registration

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Message-ID: <CABBYNZJ23E50J2gfi5NgHj_bXMuVTHk29s+BH-zMhhWmRsd0Pg@mail.gmail.com>
Date:   Wed, 3 May 2023 10:34:06 -0700
From:   Luiz Augusto von Dentz <luiz.dentz@...il.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     Johan Hovold <johan+linaro@...nel.org>,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 1/2] Bluetooth: fix debugfs registration

Hi Johan,

On Wed, May 3, 2023 at 12:04 AM Johan Hovold <johan@...nel.org> wrote:
>
> On Tue, May 02, 2023 at 04:37:51PM -0700, Luiz Augusto von Dentz wrote:
> > Hi Johan,
> >
> > On Mon, Apr 24, 2023 at 5:50 AM Johan Hovold <johan+linaro@...nel.org> wrote:
> > >
> > > Since commit ec6cef9cd98d ("Bluetooth: Fix SMP channel registration for
> > > unconfigured controllers") the debugfs interface for unconfigured
> > > controllers will be created when the controller is configured.
> > >
> > > There is however currently nothing preventing a controller from being
> > > configured multiple time (e.g. setting the device address using btmgmt)
> > > which results in failed attempts to register the already registered
> > > debugfs entries:
> > >
> > >         debugfs: File 'features' in directory 'hci0' already present!
> > >         debugfs: File 'manufacturer' in directory 'hci0' already present!
> > >         debugfs: File 'hci_version' in directory 'hci0' already present!
> > >         ...
> > >         debugfs: File 'quirk_simultaneous_discovery' in directory 'hci0' already present!
> > >
> > > Add a controller flag to avoid trying to register the debugfs interface
> > > more than once.
> > >
> > > Fixes: ec6cef9cd98d ("Bluetooth: Fix SMP channel registration for unconfigured controllers")
> > > Cc: stable@...r.kernel.org      # 4.0
> > > Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> > > ---
>
> > > diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
> > > index 632be1267288..a8785126df75 100644
> > > --- a/net/bluetooth/hci_sync.c
> > > +++ b/net/bluetooth/hci_sync.c
> > > @@ -4501,6 +4501,9 @@ static int hci_init_sync(struct hci_dev *hdev)
> > >             !hci_dev_test_flag(hdev, HCI_CONFIG))
> > >                 return 0;
> > >
> > > +       if (hci_dev_test_and_set_flag(hdev, HCI_DEBUGFS_CREATED))
> > > +               return 0;
> >
> > Can't we just use HCI_SETUP like we do with in create_basic:
> >
> >     if (hci_dev_test_flag(hdev, HCI_SETUP))
> >         hci_debugfs_create_basic(hdev);
> >
> > Actually we might as well move these checks directly inside the
> > hci_debugfs function to make sure these only take effect during the
> > setup/first init.
>
> The problem is that commit ec6cef9cd98d ("Bluetooth: Fix SMP channel
> registration for unconfigured controllers") started deferring creation
> of most parts of the debugfs interface until the controller is
> configured (e.g. as some information is not available until then).
>
> Moving everything back to setup-time would effectively revert that.

Not moving back but just doing something like:

diff --git a/net/bluetooth/hci_debugfs.c b/net/bluetooth/hci_debugfs.c
index ec0df2f9188e..a6e94c29fc5a 100644
--- a/net/bluetooth/hci_debugfs.c
+++ b/net/bluetooth/hci_debugfs.c
@@ -310,6 +310,9 @@ DEFINE_INFO_ATTRIBUTE(firmware_info, fw_info);

 void hci_debugfs_create_common(struct hci_dev *hdev)
 {
+       if (!hci_dev_test_flag(hdev, HCI_SETUP))
+               return;
+
        debugfs_create_file("features", 0444, hdev->debugfs, hdev,
                            &features_fops);
        debugfs_create_u16("manufacturer", 0444, hdev->debugfs,

> Perhaps the interface can be changed in some way so that everything is
> again registered at setup-time (e.g. with placeholder values instead of
> conditionally created attributes), but that would at least not be
> something that we could backport.
>
> > >         hci_debugfs_create_common(hdev);
> > >
> > >         if (lmp_bredr_capable(hdev))
>
> Johan



-- 
Luiz Augusto von Dentz