linux-kernel - [PATCH 5.11 446/601] HID: lenovo: Check hid_get_drvdata() returns non NULL in lenovo

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Date:   Wed, 12 May 2021 16:48:43 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Marek Behún <kabel@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Jiri Kosina <jkosina@...e.cz>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.11 446/601] HID: lenovo: Check hid_get_drvdata() returns non NULL in lenovo_event()

From: Hans de Goede <hdegoede@...hat.com>

[ Upstream commit 34348a8661e3cd67dcf6938f08c8bb77522301f7 ]

The HID lenovo probe function only attaches drvdata to one of the
USB interfaces, but lenovo_event() will get called for all USB interfaces
to which hid-lenovo is bound.

This allows a malicious device to fake being a device handled by
hid-lenovo, which generates events for which lenovo_event() has
special handling (and thus dereferences hid_get_drvdata()) on another
interface triggering a NULL pointer exception.

Add a check for hid_get_drvdata() returning NULL, avoiding this
possible NULL pointer exception.

Fixes: bc04b37ea0ec ("HID: lenovo: Add ThinkPad 10 Ultrabook Keyboard support")
Reviewed-by: Marek Behún <kabel@...nel.org>
Signed-off-by: Hans de Goede <hdegoede@...hat.com>
Signed-off-by: Jiri Kosina <jkosina@...e.cz>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/hid/hid-lenovo.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/hid/hid-lenovo.c b/drivers/hid/hid-lenovo.c
index ee175ab54281..b2596ed37880 100644
--- a/drivers/hid/hid-lenovo.c
+++ b/drivers/hid/hid-lenovo.c
@@ -508,6 +508,9 @@ static int lenovo_event_cptkbd(struct hid_device *hdev,
 static int lenovo_event(struct hid_device *hdev, struct hid_field *field,
 		struct hid_usage *usage, __s32 value)
 {
+	if (!hid_get_drvdata(hdev))
+		return 0;
+
 	switch (hdev->product) {
 	case USB_DEVICE_ID_LENOVO_CUSBKBD:
 	case USB_DEVICE_ID_LENOVO_CBTKBD:
-- 
2.30.2