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Subject: Re: [PATCH v3] Bluetooth: Don't initialize msft/aosp when using user
 channel
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <20211115220021.v3.1.I2a8b2f2e52d05ae9ead3f3dcc1dd90ef47a7acd7@changeid>
Date:   Tue, 16 Nov 2021 14:59:57 +0100
Cc:     linux-bluetooth <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>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org
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Message-Id: <E810B5F4-6334-4130-A5BD-A21F56ABD71B@holtmann.org>
References: <20211115220021.v3.1.I2a8b2f2e52d05ae9ead3f3dcc1dd90ef47a7acd7@changeid>
To:     Jesse Melhuish <melhuishj@chromium.org>
Precedence: bulk

Hi Jesse,

> 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)
> Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
> Reviewed-by: Sonny Sasaka <sonnysasaka@chromium.org>
> Signed-off-by: Jesse Melhuish <melhuishj@chromium.org>
> ---
> 
> Changes in v3:
> - Added guard around *_close calls as well.
> 
> Changes in v2:
> - Moved guard to the new home for this code.
> 
> net/bluetooth/hci_sync.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)

patch has been applied to bluetooth-next tree.

Regards

Marcel