netdev - [PATCH] Bluetooth: hci_core: fix init with HCI_QUIRK_NON_PERSISTENT

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Date:   Thu,  3 Oct 2019 17:09:32 -0700
From:   Mattijs Korpershoek <mkorpershoek@...libre.com>
To:     linux-bluetooth@...r.kernel.org
Cc:     Sean Wang <sean.wang@...iatek.com>,
        Mattijs Korpershoek <mkorpershoek@...libre.com>,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] Bluetooth: hci_core: fix init with HCI_QUIRK_NON_PERSISTENT_SETUP

Some HCI devices which have the HCI_QUIRK_NON_PERSISTENT_SETUP [1]
require a call to setup() to be ran after every open().

During the setup() stage, these devices expect the chip to acknowledge
its setup() completion via vendor specific frames.

If userspace opens() such HCI device in HCI_USER_CHANNEL [2] mode,
the vendor specific frames are never tranmitted to the driver, as
they are filtered in hci_rx_work().

Allow HCI devices which have HCI_QUIRK_NON_PERSISTENT_SETUP to process
frames if the HCI device is is HCI_INIT state.

[1] https://lore.kernel.org/patchwork/patch/965071/
[2] https://www.spinics.net/lists/linux-bluetooth/msg37345.html

Fixes: 740011cfe948 ("Bluetooth: Add new quirk for non-persistent setup settings")
Signed-off-by: Mattijs Korpershoek <mkorpershoek@...libre.com>
---
Some more background on the change follows:

The Android bluetooth stack (Bluedroid) also has a HAL implementation
which follows Linux's standard rfkill interface [1].

This implementation relies on the HCI_CHANNEL_USER feature to get
exclusive access to the underlying bluetooth device.

When testing this along with the btkmtksdio driver, the
chip appeared unresponsive when calling the following from userspace:

    struct sockaddr_hci addr;
    int fd;

    fd = socket(AF_BLUETOOTH, SOCK_RAW, BTPROTO_HCI);

    memset(&addr, 0, sizeof(addr));
    addr.hci_family = AF_BLUETOOTH;
    addr.hci_dev = 0;
    addr.hci_channel = HCI_CHANNEL_USER;

    bind(fd, (struct sockaddr *) &addr, sizeof(addr)); # device hangs

In the case of bluetooth drivers exposing QUIRK_NON_PERSISTENT_SETUP
such as btmtksdio, setup() is called each multiple times.
In particular, when userspace calls bind(), the setup() is called again
and vendor specific commands might be send to re-initialize the chip.

Those commands are filtered out by hci_core in HCI_CHANNEL_USER mode,
preventing setup() from completing successfully.

This has been tested on a 4.19 kernel based on Android Common Kernel.
It has also been compile tested on bluetooth-next.

[1] https://android.googlesource.com/platform/system/bt/+/refs/heads/master/vendor_libs/linux/interface/

 net/bluetooth/hci_core.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 04bc79359a17..5f12e8574d54 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -4440,9 +4440,20 @@ static void hci_rx_work(struct work_struct *work)
 			hci_send_to_sock(hdev, skb);
 		}

+		/* If the device has been opened in HCI_USER_CHANNEL,
+		 * the userspace has exclusive access to device.
+		 * When HCI_QUIRK_NON_PERSISTENT_SETUP is set and
+		 * device is HCI_INIT,  we still need to process
+		 * the data packets to the driver in order
+		 * to complete its setup().
+		 */
 		if (hci_dev_test_flag(hdev, HCI_USER_CHANNEL)) {
-			kfree_skb(skb);
-			continue;
+			if (!test_bit(HCI_QUIRK_NON_PERSISTENT_SETUP,
+				      &hdev->quirks) ||
+			    !test_bit(HCI_INIT, &hdev->flags)) {
+				kfree_skb(skb);
+				continue;
+			}
 		}

 		if (test_bit(HCI_INIT, &hdev->flags)) {
-- 
2.20.1