[PATCH 1/1] HID: uhid: Fix out-of-bounds write caused by raw events mismanagement

[Lee Jones <lee@kernel.org>]

Since the report ID is located within the data buffer, overwriting it
would mean that any subsequent matching could cause a disparity in
assumed allocated buffer size.  This in turn could trivially result in
an out-of-bounds condition.  To mitigate this issue, let's refuse to
overwrite a given report's data area if the ID in get_report_reply
doesn't match.

Cc: stable@vger.kernel.org
Fixes: fcfcf0deb89ec ("HID: uhid: implement feature requests")
Signed-off-by: Lee Jones <lee@kernel.org>
---
 drivers/hid/uhid.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
index 21a70420151e..a0ee4e86656f 100644
--- a/drivers/hid/uhid.c
+++ b/drivers/hid/uhid.c
@@ -262,6 +262,10 @@ static int uhid_hid_get_report(struct hid_device *hid, unsigned char rnum,
 	req = &uhid->report_buf.u.get_report_reply;
 	if (req->err) {
 		ret = -EIO;
+	} else if (rnum != req->data[0]) {
+		hid_err(hid, "Report ID mismatch - refusing to overwrite the data buffer\n");
+		ret = -EINVAL;
+		goto unlock;
 	} else {
 		ret = min3(count, (size_t)req->size, (size_t)UHID_DATA_MAX);
 		memcpy(buf, req->data, ret);
-- 
2.53.0.273.g2a3d683680-goog