CVE-2026-74285: net: Stop leased rxq before uninstalling its memory provider

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

net: Stop leased rxq before uninstalling its memory provider

netifrxqcleanupunlease() tears down the memory provider that was installed on a physical RX queue through a netkit queue lease. It currently revokes the provider's DMA mappings before stopping the physical queue:

netifmpuninstallrxq(virtrxq, p); / DMA unmap / netifmpcloserxq(physrxq->dev, rxqidx, p); / queue stop /

This inverts the ordering used by the regular teardown paths (normal device unregister and the iouring zcrx close path), which stop the queue before revoking the provider's mappings.

With the physical queue still live, its NAPI can keep consuming netiov entries from the pagepool alloc cache after the netifmpuninstallrxq() has already cleared their dmaaddr, opening a window for the device to DMA to a stale or zero address.

Fix it by swapping the two calls so the queue is stopped (and its NAPI quiesced) before the provider is uninstalled. No functional regression was observed across repeated runs of the nkqlease.py HW selftest, which exercises the lease teardown path; this was tested against fbnic QEMU emulation.