CVE-2026-64175: wifi: iwlwifi: mld: stop TX during firmware restart

From: Greg Kroah-Hartman <[email protected]>

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

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

wifi: iwlwifi: mld: stop TX during firmware restart

When iwlwifi firmware crashes (e.g., NMI_INTERRUPT_UNKNOWN on Intel
BE201/Wi-Fi 7), iwl_mld_nic_error() sets mld->fw_status.in_hw_restart
to true. However, iwl_mld_tx_from_txq() does not check this flag before
dequeuing frames from mac80211 and pushing them to the transport layer.

Since the firmware is dead, iwl_trans_tx() returns -EIO for each frame,
which then gets freed immediately. Under high-throughput conditions
(e.g., Tailscale UDP traffic or active SSH sessions), this creates a
tight dequeue-send-fail-free loop that wastes CPU cycles and generates
rapid skb allocation churn, leading to memory pressure from slab
fragmentation.

The RX path already has this guard (iwl_mld_rx_mpdu checks
in_hw_restart at rx.c:1906), and so does the TXQ allocation worker
(iwl_mld_add_txqs_wk at tx.c:156). Add the same guard to
iwl_mld_tx_from_txq() to stop all TX during firmware restart.

Frames left in mac80211's TXQs are naturally drained after restart
completes, when queue reallocation triggers iwl_mld_tx_from_txq()
via iwl_mld_add_txq_list(), or when new upper-layer traffic invokes
wake_tx_queue.

Tested on ASUS Zenbook 14 UX3405CA with Intel BE201 (Wi-Fi 7) on
kernel 6.19.5 where the firmware crashes approximately every 10-15
minutes under Tailscale traffic.

The Linux kernel CVE team has assigned CVE-2026-64175 to this issue.


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

	Issue introduced in 6.15 with commit d1e879ec600f9b3bdd253167533959facfefb17b and fixed in 6.18.34 with commit dc31c69476520bb4c2a208211a8d3c310a62c4d0
	Issue introduced in 6.15 with commit d1e879ec600f9b3bdd253167533959facfefb17b and fixed in 7.0.11 with commit 13f1786395dbbf3df73337063c798f1266be6151
	Issue introduced in 6.15 with commit d1e879ec600f9b3bdd253167533959facfefb17b and fixed in 7.1 with commit 2becb38a3e217ef2b2f42fddd7db7a25905ec291

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-2026-64175
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:
	drivers/net/wireless/intel/iwlwifi/mld/tx.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/dc31c69476520bb4c2a208211a8d3c310a62c4d0
	https://git.kernel.org/stable/c/13f1786395dbbf3df73337063c798f1266be6151
	https://git.kernel.org/stable/c/2becb38a3e217ef2b2f42fddd7db7a25905ec291