usb: chipidea: udc: fix DMA and SG cleanup in _ep_nuke()

Overview

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

usb: chipidea: udc: fix DMA and SG cleanup in _ep_nuke()

The ChipIdea UDC driver can encounter "not page aligned sg buffer" errors when a USB device is reconnected after being disconnected during an active transfer. This occurs because _ep_nuke() returns requests to the gadget layer without properly unmapping DMA buffers or cleaning up scatter-gather bounce buffers.

Root cause: When a disconnect happens during a multi-segment DMA transfer, the request's num_mapped_sgs field and sgt.sgl pointer remain set with stale values. The request is returned to the gadget driver with status -ESHUTDOWN but still has active DMA state. If the gadget driver reuses this request on reconnect without reinitializing it, the stale DMA state causes _hardware_enqueue() to skip DMA mapping (seeing non-zero num_mapped_sgs) and attempt to use freed/invalid DMA addresses, leading to alignment errors and potential memory corruption.

The normal completion path via _hardware_dequeue() properly calls usb_gadget_unmap_request_by_dev() and sglist_do_debounce() before returning the request. The _ep_nuke() path must do the same cleanup to ensure requests are returned in a clean, reusable state.

Fix: Add DMA unmapping and bounce buffer cleanup to _ep_nuke() to mirror the cleanup sequence in _hardware_dequeue():

• Call usb_gadget_unmap_request_by_dev() if num_mapped_sgs is set
• Call sglist_do_debounce() with copy=false if bounce buffer exists

This ensures that when requests are returned due to endpoint shutdown, they don't retain stale DMA mappings. The 'false' parameter to sglist_do_debounce() prevents copying data back (appropriate for shutdown path where transfer was aborted).

Affected

• Linux >= aa69a8093ff985873cb44fe1157bd6db29a20fe4 < aad97c92119cb85db105ddda4a44c86cc0748e8c
• Linux >= aa69a8093ff985873cb44fe1157bd6db29a20fe4 < 1b72b834511d17f4d069d512f78671f3f210a2f1
• Linux >= aa69a8093ff985873cb44fe1157bd6db29a20fe4 < f4fbf2d4750d12ac8525d2efac1016fa0d84d4ec
• Linux >= aa69a8093ff985873cb44fe1157bd6db29a20fe4 < e74c436f8568af1c60942469d0a2300b3ada3857
• Linux >= aa69a8093ff985873cb44fe1157bd6db29a20fe4 < cea2a1257a3b5ea3e769a445b34af13e6aa5a123
• Linux 2.6.29

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.