HID: logitech-hidpp: Fix connect event race

There is a connect event race in hidpp_probe() in these 2 lines:

	connected = hidpp_root_get_protocol_version(hidpp) == 0;
	atomic_set(&hidpp->connected, connected);

Specifically the following can happen:

1. This line from hidpp_probe() is executed:
	connected = hidpp_root_get_protocol_version(hidpp) == 0;
   and sets connected to false;

2. A connect-event packet is received and does:
	atomic_set(&hidpp->connected, true);

3. The next line from hidpp_probe() is executed:
	atomic_set(&hidpp->connected, connected);
   and sets the atomic_t back to 0 again.

4. hidpp_connect_event() runs and sees the connected device
   as disconnected because of this.

To fix this make hidpp_connect_event() query the connection status
of the device itself instead of having it rely on possibly stale
data cached in struct hidpp_device.

This series has been tested on the following devices:
Logitech Bluetooth Laser Travel Mouse (bluetooth, HID++ 1.0)
Logitech M720 Triathlon (bluetooth, HID++ 4.5)
Logitech M720 Triathlon (unifying, HID++ 4.5)
Logitech K400 Pro (unifying, HID++ 4.1)
Logitech K270 (eQUAD nano Lite, HID++ 2.0)
Logitech M185 (eQUAD nano Lite, HID++ 4.5)
Logitech LX501 keyboard (27 Mhz, HID++ builtin scroll-wheel, HID++ 1.0)
Logitech M-RAZ105 mouse (27 Mhz, HID++ extra mouse buttons, HID++ 1.0)

And by bentiss:
Logitech Touchpad T650 (unifying)
Logitech Touchpad T651 (bluetooth)
Logitech MX Master 3B (BLE)
Logitech G403 (plain USB / Gaming receiver)

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20231010102029.111003-11-hdegoede@redhat.com
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index e945e4e8180f5a6d1e2d8553cfa8b4640a84e421..4793a3236f17136c03c84d36974bb12a294bde87 100644 (file)
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -194,7 +194,6 @@ struct hidpp_device {
 
        struct work_struct work;
        struct kfifo delayed_work_fifo;
-       atomic_t connected;
        struct input_dev *delayed_input;
 
        unsigned long quirks;
@@ -3893,8 +3892,6 @@ static int hidpp_raw_hidpp_event(struct hidpp_device *hidpp, u8 *data,
        }
 
        if (unlikely(hidpp_report_is_connect_event(hidpp, report))) {
-               atomic_set(&hidpp->connected,
-                               !(report->rap.params[0] & (1 << 6)));
                if (schedule_work(&hidpp->work) == 0)
                        dbg_hid("%s: connect event already queued\n", __func__);
                return 1;
@@ -4189,12 +4186,14 @@ static struct input_dev *hidpp_allocate_input(struct hid_device *hdev)
 static void hidpp_connect_event(struct hidpp_device *hidpp)
 {
        struct hid_device *hdev = hidpp->hid_dev;
-       int ret = 0;
-       bool connected = atomic_read(&hidpp->connected);
        struct input_dev *input;
        char *name, *devm_name;
+       int ret;
 
-       if (!connected) {
+       /* Get device version to check if it is connected */
+       ret = hidpp_root_get_protocol_version(hidpp);
+       if (ret) {
+               hid_info(hidpp->hid_dev, "Disconnected\n");
                if (hidpp->battery.ps) {
                        hidpp->battery.online = false;
                        hidpp->battery.status = POWER_SUPPLY_STATUS_UNKNOWN;
@@ -4236,16 +4235,6 @@ static void hidpp_connect_event(struct hidpp_device *hidpp)
                        return;
        }
 
-       /* the device is already connected, we can ask for its name and
-        * protocol */
-       if (!hidpp->protocol_major) {
-               ret = hidpp_root_get_protocol_version(hidpp);
-               if (ret) {
-                       hid_err(hdev, "Can not get the protocol version.\n");
-                       return;
-               }
-       }
-
        if (hidpp->protocol_major >= 2) {
                u8 feature_index;
 
@@ -4395,7 +4384,6 @@ static int hidpp_probe(struct hid_device *hdev, const struct hid_device_id *id)
 {
        struct hidpp_device *hidpp;
        int ret;
-       bool connected;
        unsigned int connect_mask = HID_CONNECT_DEFAULT;
 
        /* report_fixup needs drvdata to be set before we call hid_parse */
@@ -4485,9 +4473,6 @@ static int hidpp_probe(struct hid_device *hdev, const struct hid_device_id *id)
        else
                hidpp_non_unifying_init(hidpp);
 
-       connected = hidpp_root_get_protocol_version(hidpp) == 0;
-       atomic_set(&hidpp->connected, connected);
-
        schedule_work(&hidpp->work);
        flush_work(&hidpp->work);