CVE-2026-99266: io_uring/zcrx: fix buffer offsets in areas above 4GB

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

iouring/zcrx: fix buffer offsets in areas above 4GB

iozcrxqueuecqe() computes the offset of the buffer in its area from netiovidx(), which is an unsigned int, so the shift is done in 32 bits and only the result is widened to the u64 that goes into the CQE. An area can be up to 1TB in size. For every niov beyond the first 4GB the CQE points the application at a buffer 4GB, or a multiple of that, below the one which has the data. It reads the wrong data, and then returns a buffer it doesn't own via the refill queue while the real one is never given back.