[PATCH] HID: cp2112: validate input response lengths

[Yousef Alhouseen]

cp2112_raw_event() parses transfer-status responses as a fixed seven-byte
structure without checking the report size. It also trusts the length in
data-read responses and copies that many bytes even when the received
report is shorter. A malformed USB device can use either path to trigger
out-of-bounds reads from the HID input buffer.

Reject short status responses with -EMSGSIZE. Treat truncated data
responses as zero-length reads so the waiting transfer fails instead of
timing out or copying beyond the report.

Fixes: e932d8178667 ("HID: add hid-cp2112 driver")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Yousef Alhouseen <alhouseenyousef@xxxxxxxxx>
---
 drivers/hid/hid-cp2112.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-cp2112.c b/drivers/hid/hid-cp2112.c
index 04379db93571..f2988659a5cb 100644
--- a/drivers/hid/hid-cp2112.c
+++ b/drivers/hid/hid-cp2112.c
@@ -1430,6 +1430,12 @@ static int cp2112_raw_event(struct hid_device *hdev, struct hid_report *report,
 
 	switch (data[0]) {
 	case CP2112_TRANSFER_STATUS_RESPONSE:
+		if (size < sizeof(*xfer)) {
+			dev->xfer_status = -EMSGSIZE;
+			atomic_set(&dev->xfer_avail, 1);
+			break;
+		}
+
 		hid_dbg(hdev, "xfer status: %02x %02x %04x %04x\n",
 			xfer->status0, xfer->status1,
 			be16_to_cpu(xfer->retries), be16_to_cpu(xfer->length));
@@ -1463,6 +1469,12 @@ static int cp2112_raw_event(struct hid_device *hdev, struct hid_report *report,
 		atomic_set(&dev->xfer_avail, 1);
 		break;
 	case CP2112_DATA_READ_RESPONSE:
+		if (size < 3 || data[2] > size - 3) {
+			dev->read_length = 0;
+			atomic_set(&dev->read_avail, 1);
+			break;
+		}
+
 		hid_dbg(hdev, "read response: %02x %02x\n", data[1], data[2]);
 
 		dev->read_length = data[2];
@@ -1494,4 +1506,3 @@ module_hid_driver(cp2112_driver);
 MODULE_DESCRIPTION("Silicon Labs HID USB to SMBus master bridge");
 MODULE_AUTHOR("David Barksdale <dbarksdale@xxxxxxxxxxx>");
 MODULE_LICENSE("GPL");
-
-- 
2.54.0