linux-kernel - [PATCH 2/3] HID: logitech-{dj,hidpp}: check report length

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Date:	Tue, 16 Dec 2014 01:50:15 +0100
From:	Peter Wu <peter@...ensteyn.nl>
To:	Jiri Kosina <jkosina@...e.cz>,
	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Nestor Lopez Casado <nlopezcasad@...itech.com>
Cc:	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] HID: logitech-{dj,hidpp}: check report length

Malicious USB devices can send bogus reports smaller than the expected
buffer size. Ensure that the length is valid to avoid reading out of
bounds.

For the old WTP, I do not have a HID descriptor so just check for the
minimum length in hidpp_raw_event (this can be changed to an inequality
later).

Signed-off-by: Peter Wu <peter@...ensteyn.nl>
---
Hi,

If you know that the WTP report (ID 2) has a length of 2, then you can change
"<" to "!=" and remove the paragraph from the commit message.

Kind regards,
Peter
---
 drivers/hid/hid-logitech-dj.c    | 16 +++++++++++++++-
 drivers/hid/hid-logitech-hidpp.c | 12 +++++++++---
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/hid/hid-logitech-dj.c b/drivers/hid/hid-logitech-dj.c
index c917ab6..5bc6d80 100644
--- a/drivers/hid/hid-logitech-dj.c
+++ b/drivers/hid/hid-logitech-dj.c
@@ -962,10 +962,24 @@ static int logi_dj_raw_event(struct hid_device *hdev,
 
 	switch (data[0]) {
 	case REPORT_ID_DJ_SHORT:
+		if (size != DJREPORT_SHORT_LENGTH) {
+			dev_err(&hdev->dev, "DJ report of bad size (%d)", size);
+			return false;
+		}
 		return logi_dj_dj_event(hdev, report, data, size);
 	case REPORT_ID_HIDPP_SHORT:
-		/* intentional fallthrough */
+		if (size != HIDPP_REPORT_SHORT_LENGTH) {
+			dev_err(&hdev->dev,
+				"Short HID++ report of bad size (%d)", size);
+			return false;
+		}
+		return logi_dj_hidpp_event(hdev, report, data, size);
 	case REPORT_ID_HIDPP_LONG:
+		if (size != HIDPP_REPORT_LONG_LENGTH) {
+			dev_err(&hdev->dev,
+				"Long HID++ report of bad size (%d)", size);
+			return false;
+		}
 		return logi_dj_hidpp_event(hdev, report, data, size);
 	}
 
diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index ae23dec..2315358 100644
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -992,11 +992,17 @@ static int hidpp_raw_event(struct hid_device *hdev, struct hid_report *report,
 			return 1;
 		}
 		return hidpp_raw_hidpp_event(hidpp, data, size);
+	case 0x02:
+		if (size < 2) {
+			hid_err(hdev, "Received HID report of bad size (%d)",
+				size);
+			return 1;
+		}
+		if (hidpp->quirks & HIDPP_QUIRK_CLASS_WTP)
+			return wtp_raw_event(hdev, data, size);
+		return 1;
 	}
 
-	if (hidpp->quirks & HIDPP_QUIRK_CLASS_WTP)
-		return wtp_raw_event(hdev, data, size);
-
 	return 0;
 }
 
-- 
2.1.3

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