From: Benjamin Tissoires <benjamin.tissoires@redhat.com>

Date: Wed, 10 Sep 2014 18:02:37 -0700

Subject: [PATCH] HID: rmi: check sanity of the incoming report

In the Dell XPS 13 9333, it appears that sometimes the bus get confused

and corrupts the incoming data. It fills the input report with the

sentinel value "ff". Synaptics told us that such behavior does not comes

from the touchpad itself, so we filter out such reports here.

Unfortunately, we can not simply discard the incoming data because they

may contain useful information. Most of the time, the misbehavior is

quite near the end of the report, so we can still use the valid part of

it.

Fixes:

https://bugzilla.redhat.com/show_bug.cgi?id=1123584

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

Signed-off-by: Andrew Duggan <aduggan@synaptics.com>

Signed-off-by: Jiri Kosina <jkosina@suse.cz>

---

 drivers/hid/hid-rmi.c | 44 ++++++++++++++++++++++++++++++++++++++------

 1 file changed, 38 insertions(+), 6 deletions(-)

diff --git a/drivers/hid/hid-rmi.c b/drivers/hid/hid-rmi.c

index 8389e8109218..3cccff73b9b9 100644

--- a/drivers/hid/hid-rmi.c

+++ b/drivers/hid/hid-rmi.c

@@ -320,10 +320,7 @@ static int rmi_f11_input_event(struct hid_device *hdev, u8 irq, u8 *data,

 	int offset;

 	int i;

-	if (size < hdata->f11.report_size)

-		return 0;

-

-	if (!(irq & hdata->f11.irq_mask))

+	if (!(irq & hdata->f11.irq_mask) || size <= 0)

 		return 0;

 	offset = (hdata->max_fingers >> 2) + 1;

@@ -332,9 +329,19 @@ static int rmi_f11_input_event(struct hid_device *hdev, u8 irq, u8 *data,

 		int fs_bit_position = (i & 0x3) << 1;

 		int finger_state = (data[fs_byte_position] >> fs_bit_position) &

 					0x03;

+		int position = offset + 5 * i;

+

+		if (position + 5 > size) {

+			/* partial report, go on with what we received */

+			printk_once(KERN_WARNING

+				"%s %s: Detected incomplete finger report. Finger reports may occasionally get dropped on this platform.\n",

+				 dev_driver_string(&hdev->dev),

+				 dev_name(&hdev->dev));

+			hid_dbg(hdev, "Incomplete finger report\n");

+			break;

+		}

-		rmi_f11_process_touch(hdata, i, finger_state,

-				&data[offset + 5 * i]);

+		rmi_f11_process_touch(hdata, i, finger_state, &data[position]);

 	}

 	input_mt_sync_frame(hdata->input);

 	input_sync(hdata->input);

@@ -352,6 +359,11 @@ static int rmi_f30_input_event(struct hid_device *hdev, u8 irq, u8 *data,

 	if (!(irq & hdata->f30.irq_mask))

 		return 0;

+	if (size < (int)hdata->f30.report_size) {

+		hid_warn(hdev, "Click Button pressed, but the click data is missing\n");

+		return 0;

+	}

+

 	for (i = 0; i < hdata->gpio_led_count; i++) {

 		if (test_bit(i, &hdata->button_mask)) {

 			value = (data[i / 8] >> (i & 0x07)) & BIT(0);

@@ -412,9 +424,29 @@ static int rmi_read_data_event(struct hid_device *hdev, u8 *data, int size)

 	return 1;

 }

+static int rmi_check_sanity(struct hid_device *hdev, u8 *data, int size)

+{

+	int valid_size = size;

+	/*

+	 * On the Dell XPS 13 9333, the bus sometimes get confused and fills

+	 * the report with a sentinel value "ff". Synaptics told us that such

+	 * behavior does not comes from the touchpad itself, so we filter out

+	 * such reports here.

+	 */

+

+	while ((data[valid_size - 1] == 0xff) && valid_size > 0)

+		valid_size--;

+

+	return valid_size;

+}

+

 static int rmi_raw_event(struct hid_device *hdev,

 		struct hid_report *report, u8 *data, int size)

 {

+	size = rmi_check_sanity(hdev, data, size);

+	if (size < 2)

+		return 0;

+

 	switch (data[0]) {

 	case RMI_READ_DATA_REPORT_ID:

 		return rmi_read_data_event(hdev, data, size);

-- 

1.9.3