[PATCH v2 2/2] HID: logitech-dj: Prevent REPORT_ID_DJ_SHORT related user initiated OOB write

[Lee Jones <lee@kernel.org>]

logi_dj_recv_send_report() assumes that all incoming REPORT_ID_DJ_SHORT
reports are 14 Bytes (DJREPORT_SHORT_LENGTH - 1) long.  It uses that
assumption to load the associated field's 'value' array with 14 Bytes of
data.  However, if a malicious user only sends say 1 Byte of data,
'report_count' will be 1 and only 1 Byte of memory will be allocated to
the 'value' Byte array.  When we come to populate 'value[1-13]' we will
experience an OOB write.

Signed-off-by: Lee Jones <lee@kernel.org>
---
v1 => v2: Move handling to .probe()

 drivers/hid/hid-logitech-dj.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/hid/hid-logitech-dj.c b/drivers/hid/hid-logitech-dj.c
index 32139b2561c0..a8082199d13d 100644
--- a/drivers/hid/hid-logitech-dj.c
+++ b/drivers/hid/hid-logitech-dj.c
@@ -1859,6 +1859,7 @@ static int logi_dj_probe(struct hid_device *hdev,
 			 const struct hid_device_id *id)
 {
 	struct hid_report_enum *input_report_enum;
+	struct hid_report_enum *output_report_enum;
 	struct hid_report *rep;
 	struct dj_receiver_dev *djrcv_dev;
 	struct usb_interface *intf;
@@ -1903,6 +1904,15 @@ static int logi_dj_probe(struct hid_device *hdev,
 		}
 	}
 
+	output_report_enum = &hdev->report_enum[HID_OUTPUT_REPORT];
+	rep = output_report_enum->report_id_hash[REPORT_ID_DJ_SHORT];
+
+	if (rep->maxfield < 1 || rep->field[0]->report_count != DJREPORT_SHORT_LENGTH - 1) {
+		hid_err(hdev, "Expected size of DJ short report is %d, but got %d",
+			DJREPORT_SHORT_LENGTH - 1, rep->field[0]->report_count);
+		return -EINVAL;
+	}
+
 	input_report_enum = &hdev->report_enum[HID_INPUT_REPORT];
 
 	/* no input reports, bail out */
-- 
2.53.0.983.g0bb29b3bc5-goog