ublk: make sure ubq->canceling is set when queue is frozen

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: ublk: make sure ubq->canceling is set when queue is frozen Now ublk driver depends on `ubq->canceling` for deciding if the request can be dispatched via uring_cmd & io_uring_cmd_complete_in_task(). Once ubq->canceling is set, the uring_cmd can be done via ublk_cancel_cmd() and io_uring_cmd_done(). So set ubq->canceling when queue is frozen, this way makes sure that the flag can be observed from ublk_queue_rq() reliably, and avoids use-after-free on uring_cmd.

References

• https://git.kernel.org/stable/c/7e3497d7dacb5aee69dd9be842b778083cae0e75
• https://git.kernel.org/stable/c/5491400589e7572c2d2627ed6384302f7672aa1d
• https://git.kernel.org/stable/c/9158359015f0eda00e521e35b7bc7ebce176aebf
• https://git.kernel.org/stable/c/8741d0737921ec1c03cf59aebf4d01400c2b461a