Hello,
I am working on a device which provide a CDC ECM interface.
When I connect it to an Ubuntu 8.04 desktop using 2.6.27-14 kernel, the
interface does not go up and I get the following error :
kernel: [33329.037807] usb 1-4.1: bad CDC descriptors
I found that my device send a CDC UNION descriptor with multiple slave
interfaces.
After some check I found the definition of the structure in the kernel
(include/linux/usb/cdc.h) :
/* "Union Functional Descriptor" from CDC spec 5.2.3.8 */
struct usb_cdc_union_desc {
__u8 bLength;
__u8 bDescriptorType;
__u8 bDescriptorSubType;
__u8 bMasterInterface0;
__u8 bSlaveInterface0;
/* ... and there could be other slave interfaces */
} __attribute__ ((packed));
But in function usbnet_generic_cdc_bind() (in file
drivers/net/usb/cdc_ether.c line 173), the check for the CDC UNION
descriptor is done on the exact size of the structure:
if (info->u->bLength != sizeof *info->u)
This works only if there is one single slave interface (so the bLength
is equal to the structure length).
Shouldn't it be : if (info->u->bLength < sizeof *info->u) ?
Regards
Fred
--
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It is not by improving the oil lamp that one invents the electric bulb!
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Danis Frederic Access Company
Software engineer
Mail : mailto:frederic.danis@xxxxxxxxxxxxxxxxxx
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