[PATCH 3.2 082/131] HID: logitech: perform bounds checking on device_id early enough

[Ben Hutchings]

3.2.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Jiri Kosina <jkosina@xxxxxxx>

commit ad3e14d7c5268c2e24477c6ef54bbdf88add5d36 upstream.

device_index is a char type and the size of paired_dj_deivces is 7
elements, therefore proper bounds checking has to be applied to
device_index before it is used.

We are currently performing the bounds checking in
logi_dj_recv_add_djhid_device(), which is too late, as malicious device
could send REPORT_TYPE_NOTIF_DEVICE_UNPAIRED early enough and trigger the
problem in one of the report forwarding functions called from
logi_dj_raw_event().

Fix this by performing the check at the earliest possible ocasion in
logi_dj_raw_event().

Reported-by: Ben Hawkes <hawkes@xxxxxxxxxx>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/hid/hid-logitech-dj.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

--- a/drivers/hid/hid-logitech-dj.c
+++ b/drivers/hid/hid-logitech-dj.c
@@ -230,13 +230,6 @@ static void logi_dj_recv_add_djhid_devic
 		return;
 	}
 
-	if ((dj_report->device_index < DJ_DEVICE_INDEX_MIN) ||
-	    (dj_report->device_index > DJ_DEVICE_INDEX_MAX)) {
-		dev_err(&djrcv_hdev->dev, "%s: invalid device index:%d\n",
-			__func__, dj_report->device_index);
-		return;
-	}
-
 	if (djrcv_dev->paired_dj_devices[dj_report->device_index]) {
 		/* The device is already known. No need to reallocate it. */
 		dbg_hid("%s: device is already known\n", __func__);
@@ -713,6 +706,12 @@ static int logi_dj_raw_event(struct hid_
 	 * device (via hid_input_report() ) and return 1 so hid-core does not do
 	 * anything else with it.
 	 */
+	if ((dj_report->device_index < DJ_DEVICE_INDEX_MIN) ||
+	    (dj_report->device_index > DJ_DEVICE_INDEX_MAX)) {
+		dev_err(&hdev->dev, "%s: invalid device index:%d\n",
+				__func__, dj_report->device_index);
+		return false;
+	}
 
 	spin_lock_irqsave(&djrcv_dev->lock, flags);
 	if (dj_report->report_id == REPORT_ID_DJ_SHORT) {

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