[PATCH] USB: fix gathering of interface associations

Daniel Mack zonque at gmail.com
Sun Jun 10 22:31:15 CEST 2012

TEAC's UD-H01 (and probably other devices) have a gap in the interface
number allocation in their descriptors:

  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength          220
    bNumInterfaces          3
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
    Interface Association:
      bLength                 8
      bDescriptorType        11
      bFirstInterface         2
      bInterfaceCount         2
      bFunctionClass          1 Audio
      bFunctionSubClass       0
      bFunctionProtocol      32
      iFunction               4
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        2
      bAlternateSetting       0

Once a configuration is selected on this device, usb_set_configuration()
walks the known interfaces of a given configuration and calls find_iad()
on each of them to set the interface association pointer the interface
is included in.

The problem here is that the loop varibale index is taken for the
interface number in the comparison logic that gathers the association.
Which is fine as long as the descriptors are sane.

In the case above, however, the logic gets out of sync and the
interface association fields of all interfaces beyond the interface
number gap are wrong.

Fix this by passing the interface's bInterfaceNumber to find_iad()

Signed-off-by: Daniel Mack <zonque at gmail.com>
Reported-by: bEN <ml_all at circa.be>
Reported-by: Ivan Perrone <ivanperrone at hotmail.com>
Tested-by: Sergio Tabanelli <sergio.tabanelli at gmail.com>
Cc: <stable at kernel.org>
 drivers/usb/core/message.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index b548cf1..bdd1c67 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -1838,7 +1838,6 @@ free_interfaces:
 		intfc = cp->intf_cache[i];
 		intf->altsetting = intfc->altsetting;
 		intf->num_altsetting = intfc->num_altsetting;
-		intf->intf_assoc = find_iad(dev, cp, i);
 		alt = usb_altnum_to_altsetting(intf, 0);
@@ -1851,6 +1850,8 @@ free_interfaces:
 		if (!alt)
 			alt = &intf->altsetting[0];
+		intf->intf_assoc =
+			find_iad(dev, cp, alt->desc.bInterfaceNumber);
 		intf->cur_altsetting = alt;
 		usb_enable_interface(dev, intf, true);
 		intf->dev.parent = &dev->dev;


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