CVE-2026-64331
Description
In the Linux kernel, the following vulnerability has been resolved:
usbip: vudc: fix NULL deref in vep_dequeue()
vep_alloc_request() wasn't initializing vrequest->udc, so cancellations
on the FunctionFS AIO path were arriving in vep_dequeue without a valid
UDC reference.
Since vrequest->udc is never actually properly used anywhere, we opt to
remove it, and update vep_dequeue to obtain a reference to the udc with
ep_to_vudc(), consistent with the other vep_ ops.
AFAICT this bug has existed for ~10 years. Seems that nobody has really
stressed the FunctionFS AIO path on usbip's vudc.
I tested this fix in a QEMU aarch64 guest driving FunctionFS endpoints
via AIO. Before the fix, running `usbip attach` from the host would
cause the guest to oops with the following backtrace:
Call trace:
vep_dequeue+0x1c/0xe4 (P)
usb_ep_dequeue+0x14/0x20
ffs_aio_cancel+0x24/0x34
__arm64_sys_io_cancel+0xb0/0x124
do_el0_svc+0x68/0x100
el0_svc+0x18/0x5c
el0t_64_sync_handler+0x98/0xdc
el0t_64_sync+0x154/0x158