AZL-75147

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

iouring/poll: correctly handle iopoll_add() return value on update

When the core of iouring was updated to handle completions consistently and with fixed return codes, the POLLREMOVE opcode with updates got slightly broken. If a POLLADD is pending and then POLLREMOVE is used to update the events of that request, if that update causes the POLL_ADD to now trigger, then that completion is lost and a CQE is never posted.

Additionally, ensure that if an update does cause an existing POLLADD to complete, that the completion value isn't always overwritten with -ECANCELED. For that case, whatever iopoll_add() set the value to should just be retained.