CVE-2025-21776

In the Linux kernel, the following vulnerability has been resolved:

USB: hub: Ignore non-compliant devices with too many configs or interfaces

Robert Morris created a test program which can cause
usb_hub_to_struct_hub() to dereference a NULL or inappropriate
pointer:

Oops: general protection fault, probably for non-canonical address
0xcccccccccccccccc: 0000 [#1] SMP DEBUG_PAGEALLOC PTI
CPU: 7 UID: 0 PID: 117 Comm: kworker/7:1 Not tainted 6.13.0-rc3-00017-gf44d154d6e3d #14
Hardware name: FreeBSD BHYVE/BHYVE, BIOS 14.0 10/17/2021
Workqueue: usb_hub_wq hub_event
RIP: 0010:usb_hub_adjust_deviceremovable+0x78/0x110
...
Call Trace:
 <TASK>
 ? die_addr+0x31/0x80
 ? exc_general_protection+0x1b4/0x3c0
 ? asm_exc_general_protection+0x26/0x30
 ? usb_hub_adjust_deviceremovable+0x78/0x110
 hub_probe+0x7c7/0xab0
 usb_probe_interface+0x14b/0x350
 really_probe+0xd0/0x2d0
 ? __pfx___device_attach_driver+0x10/0x10
 __driver_probe_device+0x6e/0x110
 driver_probe_device+0x1a/0x90
 __device_attach_driver+0x7e/0xc0
 bus_for_each_drv+0x7f/0xd0
 __device_attach+0xaa/0x1a0
 bus_probe_device+0x8b/0xa0
 device_add+0x62e/0x810
 usb_set_configuration+0x65d/0x990
 usb_generic_driver_probe+0x4b/0x70
 usb_probe_device+0x36/0xd0

The cause of this error is that the device has two interfaces, and the
hub driver binds to interface 1 instead of interface 0, which is where
usb_hub_to_struct_hub() looks.

We can prevent the problem from occurring by refusing to accept hub
devices that violate the USB spec by having more than one
configuration or interface.