[PATCH] USB: Fix up bogus bInterval values in endpoint descriptors

This patch (as904) adds code to check for endpoint descriptor bInterval
values outside the legal limits.  Illegal values are set to 32 ms, which
seems like a reasonable default.

This fixes Bugzilla #8432.

Signed-off-by: Alan Stern <[email protected]>

---

Index: usb-2.6/drivers/usb/core/config.c
===================================================================
--- usb-2.6.orig/drivers/usb/core/config.c
+++ usb-2.6/drivers/usb/core/config.c
@@ -1,4 +1,5 @@
 #include <linux/usb.h>
+#include <linux/usb/ch9.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
@@ -49,7 +50,7 @@ static int usb_parse_endpoint(struct dev
 	unsigned char *buffer0 = buffer;
 	struct usb_endpoint_descriptor *d;
 	struct usb_host_endpoint *endpoint;
-	int n, i;
+	int n, i, j;
 
 	d = (struct usb_endpoint_descriptor *) buffer;
 	buffer += d->bLength;
@@ -84,6 +85,45 @@ static int usb_parse_endpoint(struct dev
 	memcpy(&endpoint->desc, d, n);
 	INIT_LIST_HEAD(&endpoint->urb_list);
 
+	/* If the bInterval value is outside the legal range,
+	 * set it to a default value: 32 ms */
+	i = 0;		/* i = min, j = max, n = default */
+	j = 255;
+	if (usb_endpoint_xfer_int(d)) {
+		i = 1;
+		switch (to_usb_device(ddev)->speed) {
+		case USB_SPEED_HIGH:
+			n = 9;		/* 32 ms = 2^(9-1) uframes */
+			j = 16;
+			break;
+		default:		/* USB_SPEED_FULL or _LOW */
+			/* For low-speed, 10 ms is the official minimum.
+			 * But some "overclocked" devices might want faster
+			 * polling so we'll allow it. */
+			n = 32;
+			break;
+		}
+	} else if (usb_endpoint_xfer_isoc(d)) {
+		i = 1;
+		j = 16;
+		switch (to_usb_device(ddev)->speed) {
+		case USB_SPEED_HIGH:
+			n = 9;		/* 32 ms = 2^(9-1) uframes */
+			break;
+		default:		/* USB_SPEED_FULL */
+			n = 6;		/* 32 ms = 2^(6-1) frames */
+			break;
+		}
+	}
+	if (d->bInterval < i || d->bInterval > j) {
+		dev_warn(ddev, "config %d interface %d altsetting %d "
+		    "endpoint 0x%X has an invalid bInterval %d, "
+		    "changing to %d\n",
+		    cfgno, inum, asnum,
+		    d->bEndpointAddress, d->bInterval, n);
+		endpoint->desc.bInterval = n;
+	}
+
 	/* Skip over any Class Specific or Vendor Specific descriptors;
 	 * find the next endpoint or interface descriptor */
 	endpoint->extra = buffer;


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