Re: [PATCH v1] Bluetooth: hci_release_dev: disable delayed devcoredump work

[Aby Sam Ross <abysamross@gmail.com>]

On Tue, Mar 24, 2026 at 04:42:21PM -0400, Luiz Augusto von Dentz wrote:
> Hi Aby,
> 
> On Sun, Mar 22, 2026 at 5:09 PM Aby Sam Ross <abysamross@gmail.com> wrote:
> >
> > It is not necessary that the pending delayed hci devcoredump timeout
> > work, hdev->dump.dump_timeout, submitted to the hdev->workqueue by the
> > bluetooth devcoredump state machine,
> >         hci_devcd_rx()
> >                 hci_devcd_handle_pkt_init()
> > will be reset by it or by the timeout func hci_devcd_timeout(), using
> > hci_devcd_reset(), before destroying the workqueue or before the hci
> > device is freed up in hci_release_dev().
> >
> > In this bug the active delayed devcoredump timeout work's timer object
> > is active when the memory associated with the hci device is freed up in
> > hci_release_dev() causing the ODEBUG WARNING.
> >
> > Make sure that the delayed devcoredump timeout work is disabled before
> > the hdev->workqueue is destroyed and before the hdev memory is freed in
> > hci_release_dev().
> >
> > Tested the change with the syzbot reproducer that uses vhci device
> > locally on x86_64 and on syzbot portal as well. Ran kselftest with net
> > target.
> >
> > Fixes: 9695ef876fd1 ("Bluetooth: Add support for hci devcoredump")
> > Reported-by: syzbot+b170dbf55520ebf5969a@syzkaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=b170dbf55520ebf5969a
> > Tested-by: syzbot+b170dbf55520ebf5969a@syzkaller.appspotmail.com
> > Signed-off-by: Aby Sam Ross <abysamross@gmail.com>
> > ---
> >  net/bluetooth/hci_core.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> > index 01f8ceeb1c0c..1c7ee2a33337 100644
> > --- a/net/bluetooth/hci_core.c
> > +++ b/net/bluetooth/hci_core.c
> > @@ -2747,6 +2747,9 @@ void hci_release_dev(struct hci_dev *hdev)
> >         kfree_const(hdev->hw_info);
> >         kfree_const(hdev->fw_info);
> >
> > +       if (hdev->dump.supported)
> > +               disable_delayed_work_sync(&hdev->dump.dump_timeout);
> > +
> >         destroy_workqueue(hdev->workqueue);
> >         destroy_workqueue(hdev->req_workqueue);
> >
> > --
> > 2.53.0
> >
> 
> https://sashiko.dev/#/patchset/20260322210849.68743-1-abysamross%40gmail.com
> 
> Both points seems valid, that perhaps the dump shouldn't be attached
> to hdev object since it maybe necessary to unregister the hdev as part
> of devcoredump handling, anyway if it is required then upon unregister
> it shall actually cleanup the dump object as well.
> 
> -- 
> Luiz Augusto von Dentz

Hi Luiz,

From what I see hci_unregister_dev() is called by all bluetooth drivers that use
hci_devcd_init(). Please correct me if I am wrong.

So we can either make hci_devcd_free() non-static and then call it from
hci_unregister_dev()
OR
Do vfree(hdev->dump.head) followed by disabling the delayed devcoredump timeout
work in hci_unregister_dev()

And then destroy the workqueue(dump_rx)?