Patch "Input: ims-psu - check if CDC union descriptor is sane" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

Input: ims-psu - check if CDC union descriptor is sane

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
input-ims-psu-check-if-cdc-union-descriptor-is-sane.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Dmitry Torokhov <[email protected]>
Date: Sat, 7 Oct 2017 11:07:47 -0700
Subject: Input: ims-psu - check if CDC union descriptor is sane

From: Dmitry Torokhov <[email protected]>

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.

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

@@ -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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/input-ims-psu-check-if-cdc-union-descriptor-is-sane.patch