[PATCH] HID: mcp2200: validate input report length

[Pengpeng Hou <pengpeng@iscas.ac.cn>]

From: Pengpeng <pengpeng@iscas.ac.cn>

mcp2200_raw_event() dispatches on the first byte of the HID input
report and overlays the READ_ALL response structure on the same buffer.
The HID core passes the actual report size to the callback, so validate
that the command byte and READ_ALL response fields are present before
reading them.

Reject truncated reports for the pending command instead of reading
beyond the current input report payload.

Signed-off-by: Pengpeng <pengpeng@iscas.ac.cn>
---
 drivers/hid/hid-mcp2200.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/hid/hid-mcp2200.c b/drivers/hid/hid-mcp2200.c
index dafdd5b4a079..d2f45892dc22 100644
--- a/drivers/hid/hid-mcp2200.c
+++ b/drivers/hid/hid-mcp2200.c
@@ -299,8 +299,19 @@ static int mcp2200_raw_event(struct hid_device *hdev, struct hid_report *report,
 	struct mcp2200 *mcp = hid_get_drvdata(hdev);
 	struct mcp_read_all_resp *all_resp;
 
+	if (size < 1) {
+		mcp->status = -EINVAL;
+		complete(&mcp->wait_in_report);
+		return 0;
+	}
+
 	switch (data[0]) {
 	case READ_ALL:
+		if (size < sizeof(*all_resp)) {
+			mcp->status = -EINVAL;
+			break;
+		}
+
 		all_resp = (struct mcp_read_all_resp *) data;
 		mcp->status = 0;
 		mcp->gpio_inval = all_resp->io_port_val_bmap;
-- 
2.43.0