[PATCH v2 resend 3/9] HID: lenovo: Check hid_get_drvdata() returns non NULL in lenovo_event()

From: Hans de Goede <hdegoede@redhat.com>
To: Jiri Kosina <jikos@kernel.org>,
	Benjamin Tissoires <benjamin.tissoires@redhat.com>,
	Alexander Kobel <a-kobel@a-kobel.de>
Cc: "Hans de Goede" <hdegoede@redhat.com>,
	"Pavel Machek" <pavel@ucw.cz>, "Marek Behún" <kabel@kernel.org>,
	linux-input@vger.kernel.org, linux-leds@vger.kernel.org
Subject: [PATCH v2 resend 3/9] HID: lenovo: Check hid_get_drvdata() returns non NULL in lenovo_event()
Date: Sun,  4 Apr 2021 10:04:26 +0200	[thread overview]
Message-ID: <20210404080432.4322-4-hdegoede@redhat.com> (raw)
In-Reply-To: <20210404080432.4322-1-hdegoede@redhat.com>

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@kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 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

