CVE-2021-47272

/// Technical description

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

usb: dwc3: gadget: Bail from dwc3_gadget_exit() if dwc->gadget is NULL

There exists a possible scenario in which dwc3_gadget_init() can fail:

during during host -> peripheral mode switch in dwc3_set_mode(), and

a pending gadget driver fails to bind. Then, if the DRD undergoes

another mode switch from peripheral->host the resulting

dwc3_gadget_exit() will attempt to reference an invalid and dangling

dwc->gadget pointer as well as call dma_free_coherent() on unmapped

DMA pointers.

The exact scenario can be reproduced as follows:

- Start DWC3 in peripheral mode

- Configure ConfigFS gadget with FunctionFS instance (or use g_ffs)

- Run FunctionFS userspace application (open EPs, write descriptors, etc)

- Bind gadget driver to DWC3's UDC

- Switch DWC3 to host mode

=> dwc3_gadget_exit() is called. usb_del_gadget() will put the

ConfigFS driver instance on the gadget_driver_pending_list

- Stop FunctionFS applicati

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References