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References: <20211108200058.v2.1.Ide934b992a0b54085a6be469d3687963a245dba9@changeid>
In-Reply-To: <20211108200058.v2.1.Ide934b992a0b54085a6be469d3687963a245dba9@changeid>
From:   Jesse Melhuish <melhuishj@chromium.org>
Date:   Thu, 11 Nov 2021 12:23:10 -0600
Message-ID: <CACGnfjS5OOWsdBQNpmJ7DFWTYkH0vYDmVeW71xY0h3LsNut1Mw@mail.gmail.com>
Subject: Re: [PATCH v2] Bluetooth: Don't initialize msft/aosp when using user channel
To:     Jesse Melhuish <melhuishj@chromium.org>
Cc:     linux-bluetooth@vger.kernel.org,
        Abhishek Pandit-Subedi <abhishekpandit@chromium.org>,
        Sonny Sasaka <sonnysasaka@chromium.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        Marcel Holtmann <marcel@holtmann.org>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org
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Pinging. LMK if something is wrong or missing here. Thanks!

On Mon, Nov 8, 2021 at 2:01 PM Jesse Melhuish <melhuishj@chromium.org> wrote:
>
> A race condition is triggered when usermode control is given to
> userspace before the kernel's MSFT query responds, resulting in an
> unexpected response to userspace's reset command.
>
> Issue can be observed in btmon:
> < HCI Command: Vendor (0x3f|0x001e) plen 2                    #3 [hci0]
>         05 01                                            ..
> @ USER Open: bt_stack_manage (privileged) version 2.22  {0x0002} [hci0]
> < HCI Command: Reset (0x03|0x0003) plen 0                     #4 [hci0]
> > HCI Event: Command Complete (0x0e) plen 5                   #5 [hci0]
>       Vendor (0x3f|0x001e) ncmd 1
>         Status: Command Disallowed (0x0c)
>         05                                               .
> > HCI Event: Command Complete (0x0e) plen 4                   #6 [hci0]
>       Reset (0x03|0x0003) ncmd 2
>         Status: Success (0x00)
>
> Signed-off-by: Jesse Melhuish <melhuishj@chromium.org>
> Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
> Reviewed-by: Sonny Sasaka <sonnysasaka@chromium.org>
> ---
>
> Changes in v2:
> - Moved guard to the new home for this code.
>
>  net/bluetooth/hci_sync.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
> index b794605dc882..5f1f59ac1813 100644
> --- a/net/bluetooth/hci_sync.c
> +++ b/net/bluetooth/hci_sync.c
> @@ -3887,8 +3887,10 @@ int hci_dev_open_sync(struct hci_dev *hdev)
>             hci_dev_test_flag(hdev, HCI_VENDOR_DIAG) && hdev->set_diag)
>                 ret = hdev->set_diag(hdev, true);
>
> -       msft_do_open(hdev);
> -       aosp_do_open(hdev);
> +       if (!hci_dev_test_flag(hdev, HCI_USER_CHANNEL)) {
> +               msft_do_open(hdev);
> +               aosp_do_open(hdev);
> +       }
>
>         clear_bit(HCI_INIT, &hdev->flags);
>
> --
> 2.31.0
>