CVE-2024-58000

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

io_uring: prevent reg-wait speculations

With *ENTEREXTARGREG instead of passing a user pointer with arguments for the waiting loop the user can specify an offset into a pre-mapped region of memory, in which case the [offset, offset + sizeof(iouringregwait)) will be intepreted as the argument.

As we address a kernel array using a user given index, it'd be a subject to speculation type of exploits. Use arrayindexnospec() to prevent that. Make sure to pass not the full region size but truncate by the maximum offset allowed considering the structure size.