linux-kernel - [PATCH 3.18 06/20] Input: ims-psu - check if CDC union descriptor is sane

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Message-Id: <20171116172722.014420653@linuxfoundation.org>
Date:   Thu, 16 Nov 2017 18:28:13 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Andrey Konovalov <andreyknvl@...gle.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Ben Hutchings <ben.hutchings@...ethink.co.uk>
Subject: [PATCH 3.18 06/20] Input: ims-psu - check if CDC union descriptor is sane

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dmitry Torokhov <dmitry.torokhov@...il.com>

commit ea04efee7635c9120d015dcdeeeb6988130cb67a upstream.

Before trying to use CDC union descriptor, try to validate whether that it
is sane by checking that intf->altsetting->extra is big enough and that
descriptor bLength is not too big and not too small.

Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: Ben Hutchings <ben.hutchings@...ethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/input/misc/ims-pcu.c |   16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

--- a/drivers/input/misc/ims-pcu.c
+++ b/drivers/input/misc/ims-pcu.c
@@ -1635,13 +1635,25 @@ ims_pcu_get_cdc_union_desc(struct usb_in
 		return NULL;
 	}
 
-	while (buflen > 0) {
+	while (buflen >= sizeof(*union_desc)) {
 		union_desc = (struct usb_cdc_union_desc *)buf;
 
+		if (union_desc->bLength > buflen) {
+			dev_err(&intf->dev, "Too large descriptor\n");
+			return NULL;
+		}
+
 		if (union_desc->bDescriptorType == USB_DT_CS_INTERFACE &&
 		    union_desc->bDescriptorSubType == USB_CDC_UNION_TYPE) {
 			dev_dbg(&intf->dev, "Found union header\n");
-			return union_desc;
+
+			if (union_desc->bLength >= sizeof(*union_desc))
+				return union_desc;
+
+			dev_err(&intf->dev,
+				"Union descriptor to short (%d vs %zd\n)",
+				union_desc->bLength, sizeof(*union_desc));
+			return NULL;
 		}
 
 		buflen -= union_desc->bLength;