> I think it's overkill. Despite what I wrote before, that test patch you
> sent out yesterday looked pretty good. Config options and blacklists
> should be avoided if at all possible, especially for stupid little things
> like this.
>
> When the string descriptor routines encounter a result that has both type
> and length equal to 0, cautious scanning seems like a good way to proceed.
> In other words, I like option (C) but not (A) or (B). And I would leave
> out the part about suggesting an email to the list, since it's not needed
> if no one is maintaining a black/whitelist.
How about this? I tweaked usb_string_sub while I was there so it only ever
returns even lengths (in the case of an odd length, usb_string used to read
the last, uninitialised character - better to fix this in usb_string_sub).
Now I think about it, the debug message should also print the descriptor index.
If you are happy with this I will make that change and send the patch to Greg.
Ciao,
Duncan.
Index: local-tree/drivers/usb/core/message.c
===================================================================
--- local-tree.orig/drivers/usb/core/message.c 2004-09-23 23:52:51.736541393 +0200
+++ local-tree/drivers/usb/core/message.c 2004-09-24 02:06:57.401859258 +0200
@@ -17,6 +17,8 @@
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/timer.h>
+#include <linux/ctype.h>
+#include <linux/device.h>
#include <asm/byteorder.h>
#include "hcd.h" /* for usbcore internals */
@@ -623,6 +625,20 @@
return result;
}
+static void usb_try_string_workarounds(unsigned char *buf, int *length)
+{
+ int newlength, oldlength = *length;
+
+ for(newlength = 2; newlength + 1 < oldlength; newlength += 2)
+ if (!isprint(buf[newlength]) || buf[newlength + 1])
+ break;
+
+ if (newlength > 2) {
+ buf[0] = newlength;
+ *length = newlength;
+ }
+}
+
static int usb_string_sub(struct usb_device *dev, unsigned int langid,
unsigned int index, unsigned char *buf)
{
@@ -634,19 +650,26 @@
/* If that failed try to read the descriptor length, then
* ask for just that many bytes */
- if (rc < 0) {
+ if (rc < 2) {
rc = usb_get_string(dev, langid, index, buf, 2);
if (rc == 2)
rc = usb_get_string(dev, langid, index, buf, buf[0]);
}
- if (rc >= 0) {
+ if (rc >= 2) {
+ if (!buf[0] && !buf[1])
+ usb_try_string_workarounds(buf, &rc);
+
/* There might be extra junk at the end of the descriptor */
if (buf[0] < rc)
rc = buf[0];
- if (rc < 2)
- rc = -EINVAL;
+
+ rc = rc - (rc & 1); /* force a multiple of two */
}
+
+ if (rc < 2)
+ rc = (rc < 0 ? rc : -EINVAL);
+
return rc;
}
@@ -677,7 +700,7 @@
int usb_string(struct usb_device *dev, int index, char *buf, size_t size)
{
unsigned char *tbuf;
- int err;
+ int descriptor_type, err;
unsigned int u, idx;
if (size <= 0 || !buf || !index)
@@ -712,6 +735,8 @@
if (err < 0)
goto errout;
+ descriptor_type = tbuf[1];
+
size--; /* leave room for trailing NULL char in output buffer */
for (idx = 0, u = 2; u < err; u += 2) {
if (idx >= size)
@@ -724,6 +749,9 @@
buf[idx] = 0;
err = idx;
+ if (descriptor_type != USB_DT_STRING)
+ dev_dbg(&dev->dev, "string \"%s\" has wrong descriptor type %02x\n",
buf, descriptor_type);
+
errout:
kfree(tbuf);
return err;
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