[patch 019/114] USB: usb_get_string should check the descriptor type

Greg KH
2009-03-14T01:27:08Z

[-- Attachment #1: usb-usb_get_string-should-check-the-descriptor-type.patch --]
[-- Type: text/plain, Size: 1803 bytes --]

2.6.28-stable review patch. If anyone has any objections, please let us know.

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

From: Alan Stern <stern@rowland.harvard.edu>

commit 67f5a4ba9741fcef3f4db3509ad03565d9e33af2 upstream.

This patch (as1218) fixes a problem with a radio-control joystick used
in the "walkera 4#3" helicopter. This device responds to the initial
Get-String-Descriptor request for string 0 (which is really the list
of supported languages) by sending its config descriptor! The
usb_get_string() routine needs to check whether it got the right
type of descriptor.

Oddly enough, this sort of check is already present in
usb_get_descriptor(). The patch changes the error code from -EPROTO
to -ENODATA, because -EPROTO shows up in so many other contexts to
indicate a hardware failure rather than a firmware error.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Guillermo Jarabo <williamjap@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/usb/core/message.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -651,7 +651,7 @@ int usb_get_descriptor(struct usb_device
if (result <= 0 && result != -ETIMEDOUT)
continue;
if (result > 1 && ((u8 *)buf)[1] != type) {
- result = -EPROTO;
+ result = -ENODATA;
continue;
}
break;
@@ -694,8 +694,13 @@ static int usb_get_string(struct usb_dev
USB_REQ_GET_DESCRIPTOR, USB_DIR_IN,
(USB_DT_STRING << 8) + index, langid, buf, size,
USB_CTRL_GET_TIMEOUT);
- if (!(result == 0 || result == -EPIPE))
- break;
+ if (result == 0 || result == -EPIPE)
+ continue;
+ if (result > 1 && ((u8 *) buf)[1] != USB_DT_STRING) {
+ result = -ENODATA;
+ continue;
+ }
+ break;
}
return result;
}