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

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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

net: Stop leased rxq before uninstalling its memory provider

netif_rxq_cleanup_unlease() 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:

  __netif_mp_uninstall_rxq(virt_rxq, p);            /* DMA unmap */
  __netif_mp_close_rxq(phys_rxq->dev, rxq_idx, p);  /* queue stop */

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

With the physical queue still live, its NAPI can keep consuming
net_iov entries from the page_pool alloc cache after the
__netif_mp_uninstall_rxq() has already cleared their dma_addr,
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 nk_qlease.py
HW selftest, which exercises the lease teardown path; this was
tested against fbnic QEMU emulation.

The Linux kernel CVE team has assigned CVE-2026-74285 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 7.1 with commit 5602ad61ebee99c83081fba1aaf5814736edc3e7 and fixed in 7.1.5 with commit 03f4c6ed3cffbfce0b85a3a0193d08a46692a9f8
	Issue introduced in 7.1 with commit 5602ad61ebee99c83081fba1aaf5814736edc3e7 and fixed in 7.2-rc1 with commit 37314c9dbe95b4d924c7b61aaf563cec4f4e4133

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-74285
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/core/netdev_rx_queue.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/03f4c6ed3cffbfce0b85a3a0193d08a46692a9f8
	https://git.kernel.org/stable/c/37314c9dbe95b4d924c7b61aaf563cec4f4e4133