Medium · published July 25, 2026
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
| Product | Versions | Fixed in |
|---|---|---|
| linux/linux_kernel | ≥ 4.7, < 5.10.261 | 5.10.261 |
| linux/linux_kernel | ≥ 5.11, < 5.15.212 | 5.15.212 |
| linux/linux_kernel | ≥ 5.16, < 6.1.178 | 6.1.178 |
| linux/linux_kernel | ≥ 6.2, < 6.6.145 | 6.6.145 |
| linux/linux_kernel | ≥ 6.7, < 6.12.96 | 6.12.96 |
| linux/linux_kernel | ≥ 6.13, < 6.18.39 | 6.18.39 |
| linux/linux_kernel | ≥ 6.19, < 7.1.4 | 7.1.4 |
| linux/linux_kernel | all versions | — |
| linux/linux_kernel | all versions | — |