Syzbot has identified a bug in usbcore (see the Closes: tag below) caused by our assumption that the reserved bits in an endpoint descriptor's bEndpointAddress field will always be 0. As a result of the bug, the endpoint_is_duplicate() routine in config.c (and possibly other routines as well) may believe that two descriptors are for distinct endpoints, even though they have the same direction and endpoint number. This can lead to confusion, including the bug identified by syzbot (two descriptors with matching endpoint numbers and directions, where one was interrupt and the other was bulk). To fix the bug, we will clear the reserved bits in bEndpointAddress when we parse the descriptor. (Note that both the USB-2.0 and USB-3.1 specs say these bits are "Reserved, reset to zero".) This requires us to make a copy of the descriptor earlier in usb_parse_endpoint() and use the copy instead of the original when checking for duplicates. Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> Reported-and-tested-by: syzbot+8693a0bb9c10b554272a@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://lore.kernel.org/linux-usb/0000000000003d868e061bc0f554@xxxxxxxxxx/ Fixes: 0a8fd1346254 ("USB: fix problems with duplicate endpoint addresses") CC: Oliver Neukum <oneukum@xxxxxxxx> CC: stable@xxxxxxxxxxxxxxx --- This should also fix the bug that was reported for the usbtmc driver recently. drivers/usb/core/config.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) Index: usb-devel/drivers/usb/core/config.c =================================================================== --- usb-devel.orig/drivers/usb/core/config.c +++ usb-devel/drivers/usb/core/config.c @@ -291,6 +291,20 @@ static int usb_parse_endpoint(struct dev if (ifp->desc.bNumEndpoints >= num_ep) goto skip_to_next_endpoint_or_interface_descriptor; + /* Save a copy of the descriptor and use it instead of the original */ + endpoint = &ifp->endpoint[ifp->desc.bNumEndpoints]; + memcpy(&endpoint->desc, d, n); + d = &endpoint->desc; + + /* Clear the reserved bits in bEndpointAddress */ + i = d->bEndpointAddress & + (USB_ENDPOINT_DIR_MASK | USB_ENDPOINT_NUMBER_MASK); + if (i != d->bEndpointAddress) { + dev_notice(ddev, "config %d interface %d altsetting %d has an endpoint descriptor with address 0x%X, changing to 0x%X\n", + cfgno, inum, asnum, d->bEndpointAddress, i); + endpoint->desc.bEndpointAddress = i; + } + /* Check for duplicate endpoint addresses */ if (config_endpoint_is_duplicate(config, inum, asnum, d)) { dev_notice(ddev, "config %d interface %d altsetting %d has a duplicate endpoint with address 0x%X, skipping\n", @@ -308,10 +322,8 @@ static int usb_parse_endpoint(struct dev } } - endpoint = &ifp->endpoint[ifp->desc.bNumEndpoints]; + /* Accept this endpoint */ ++ifp->desc.bNumEndpoints; - - memcpy(&endpoint->desc, d, n); INIT_LIST_HEAD(&endpoint->urb_list); /*
