[PATCH 08/10] HID: prodikeys: validate fixed-format MIDI reports

[Jiale Yao]

The HID core invokes raw_event callbacks before validating the report
length.  Prodikeys reports 0x01 and 0x04 are passed to handlers that always
read bytes one through three, regardless of the supplied size.  A truncated
report can therefore cause an out-of-bounds read.

Require four bytes for the two fixed-format reports.  Keep report 0x03 on
its existing variable-length path, which derives the number of note pairs
from size and only accesses complete pairs.

Commit 47669bec44fe ("HID: asus: refactor the two workqueues and init
sequence") added the same kind of raw_event length validation to hid-asus.

Fixes: 3a370ca1dcf8 ("HID: Prodikeys PC-MIDI HID Driver")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jiale Yao <yaojiale02@xxxxxxx>
---
 drivers/hid/hid-prodikeys.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-prodikeys.c b/drivers/hid/hid-prodikeys.c
index fba01e4fcab1..bf5add40d3e1 100644
--- a/drivers/hid/hid-prodikeys.c
+++ b/drivers/hid/hid-prodikeys.c
@@ -772,8 +772,13 @@ static int pk_raw_event(struct hid_device *hdev, struct hid_report *report,
 		if (report->id == data[0])
 			switch (report->id) {
 			case 0x01: /* midi keys (qwerty)*/
-			case 0x03: /* midi keyboard (musical)*/
 			case 0x04: /* extra/midi keys (qwerty)*/
+				if (size < 4)
+					break;
+				ret = pcmidi_handle_report(pm, report->id,
+							   data, size);
+				break;
+			case 0x03: /* midi keyboard (musical)*/
 				ret = pcmidi_handle_report(pm,
 						report->id, data, size);
 				break;
-- 
2.34.1