USB: validate wMaxPacketValue entries in endpoint descriptors

Erroneous or malicious endpoint descriptors may have non-zero bits in
reserved positions, or out-of-bounds values.  This patch helps prevent
these from causing problems by bounds-checking the wMaxPacketValue
entries in endpoint descriptors and capping the values at the maximum
allowed.

This issue was first discovered and tests were conducted by Jake Lamberson
<[email protected]>, an intern working for Rosie Hall.

Signed-off-by: Alan Stern <[email protected]>
Reported-by: roswest <[email protected]>
Tested-by: roswest <[email protected]>
CC: <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: AlanStern

drivers/usb/core/config.c

@@ -171,6 +171,31 @@ static void usb_parse_ss_endpoint_companion(struct device *ddev, int cfgno,
 							ep, buffer, size);
 }
 
+static const unsigned short low_speed_maxpacket_maxes[4] = {
+	[USB_ENDPOINT_XFER_CONTROL] = 8,
+	[USB_ENDPOINT_XFER_ISOC] = 0,
+	[USB_ENDPOINT_XFER_BULK] = 0,
+	[USB_ENDPOINT_XFER_INT] = 8,
+};
+static const unsigned short full_speed_maxpacket_maxes[4] = {
+	[USB_ENDPOINT_XFER_CONTROL] = 64,
+	[USB_ENDPOINT_XFER_ISOC] = 1023,
+	[USB_ENDPOINT_XFER_BULK] = 64,
+	[USB_ENDPOINT_XFER_INT] = 64,
+};
+static const unsigned short high_speed_maxpacket_maxes[4] = {
+	[USB_ENDPOINT_XFER_CONTROL] = 64,
+	[USB_ENDPOINT_XFER_ISOC] = 1024,
+	[USB_ENDPOINT_XFER_BULK] = 512,
+	[USB_ENDPOINT_XFER_INT] = 1023,
+};
+static const unsigned short super_speed_maxpacket_maxes[4] = {
+	[USB_ENDPOINT_XFER_CONTROL] = 512,
+	[USB_ENDPOINT_XFER_ISOC] = 1024,
+	[USB_ENDPOINT_XFER_BULK] = 1024,
+	[USB_ENDPOINT_XFER_INT] = 1024,
+};
+
 static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum,
     int asnum, struct usb_host_interface *ifp, int num_ep,
     unsigned char *buffer, int size)
@@ -179,6 +204,8 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum,
 	struct usb_endpoint_descriptor *d;
 	struct usb_host_endpoint *endpoint;
 	int n, i, j, retval;
+	unsigned int maxp;
+	const unsigned short *maxpacket_maxes;
 
 	d = (struct usb_endpoint_descriptor *) buffer;
 	buffer += d->bLength;
@@ -286,16 +313,49 @@ static int usb_parse_endpoint(struct device *ddev, int cfgno, int inum,
 			endpoint->desc.wMaxPacketSize = cpu_to_le16(8);
 	}
 
+	/* Validate the wMaxPacketSize field */
+	maxp = usb_endpoint_maxp(&endpoint->desc);
+
+	/* Find the highest legal maxpacket size for this endpoint */
+	i = 0;		/* additional transactions per microframe */
+	switch (to_usb_device(ddev)->speed) {
+	case USB_SPEED_LOW:
+		maxpacket_maxes = low_speed_maxpacket_maxes;
+		break;
+	case USB_SPEED_FULL:
+		maxpacket_maxes = full_speed_maxpacket_maxes;
+		break;
+	case USB_SPEED_HIGH:
+		/* Bits 12..11 are allowed only for HS periodic endpoints */
+		if (usb_endpoint_xfer_int(d) || usb_endpoint_xfer_isoc(d)) {
+			i = maxp & (BIT(12) | BIT(11));
+			maxp &= ~i;
+		}
+		/* fallthrough */
+	default:
+		maxpacket_maxes = high_speed_maxpacket_maxes;
+		break;
+	case USB_SPEED_SUPER:
+	case USB_SPEED_SUPER_PLUS:
+		maxpacket_maxes = super_speed_maxpacket_maxes;
+		break;
+	}
+	j = maxpacket_maxes[usb_endpoint_type(&endpoint->desc)];
+
+	if (maxp > j) {
+		dev_warn(ddev, "config %d interface %d altsetting %d endpoint 0x%X has invalid maxpacket %d, setting to %d\n",
+		    cfgno, inum, asnum, d->bEndpointAddress, maxp, j);
+		maxp = j;
+		endpoint->desc.wMaxPacketSize = cpu_to_le16(i | maxp);
+	}
+
 	/*
 	 * Some buggy high speed devices have bulk endpoints using
 	 * maxpacket sizes other than 512.  High speed HCDs may not
 	 * be able to handle that particular bug, so let's warn...
 	 */
 	if (to_usb_device(ddev)->speed == USB_SPEED_HIGH
 			&& usb_endpoint_xfer_bulk(d)) {
-		unsigned maxp;
-
-		maxp = usb_endpoint_maxp(&endpoint->desc) & 0x07ff;
 		if (maxp != 512)
 			dev_warn(ddev, "config %d interface %d altsetting %d "
 				"bulk endpoint 0x%X has invalid maxpacket %d\n",