DEBIAN-CVE-2026-99130: Debian/linux vulnerability

In the Linux kernel, the following vulnerability has been resolved: iouring/cancel: don't spin on local work the task can't run iouringcancelgeneric() refuses to sleep while any ring on the exiting task's tctx has local work pending. It assumes the task is that ring's submitter and that the next iouringtrycancelrequests() pass will run the work. This does not hold for a ring that was still IORINGSETUPRDISABLED when the task got its tctx node from iouringcreate() or ioringfdregister(). The submitter is set later by IORINGREGISTERENABLERINGS, possibly from another task, and only the submitter may run local work on an IORINGSETUPDEFERTASKRUN ring. To the exiting task the work stays pending forever, the loop never reaches schedule(), and the task trips the WARNONONCE() once and then spins in doexit(). An unprivileged user can set this up at will by creating a disabled ring, having a child enable it and stop, posting to the ring with IORINGOPMSGRING and exiting with a request in flight that only the child can complete. The exiting thread burns a CPU until the child runs or dies, and with paniconwarn set the WARN panics the kernel. Fix by skipping the sleep only when ioalloweddefertwrun() allows the task to run the work. This is reasonable since work it cannot run cannot complete any of its requests either, so nothing is lost by sleeping. Drop the WARNONONCE() since handing a disabled ring to another thread is a supported scenario, not a bug state.