CVE-2026-64255: wifi: iwlwifi: mld: validate sta_mask before ffs() in BA session handlers

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

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

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

wifi: iwlwifi: mld: validate sta_mask before ffs() in BA session handlers

Three BA session handlers use ffs(ba_data->sta_mask) - 1 to derive a
station ID without checking that sta_mask is non-zero. When sta_mask is
zero, ffs() returns 0 and the subtraction wraps to 0xFFFFFFFF, causing
an out-of-bounds access on fw_id_to_link_sta[].

Add WARN_ON_ONCE(!ba_data->sta_mask) guards before each ffs() call,
consistent with the existing check in iwl_mld_ampdu_rx_start().

The Linux kernel CVE team has assigned CVE-2026-64255 to this issue.


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

	Fixed in 6.18.38 with commit 1de92789ce31e46fa7e7d8e89c90b19cdb1c103b
	Fixed in 7.1.3 with commit fe7f339f63c9dc4ca546ed7ac38ba4bb3a99dcfc
	Fixed in 7.2-rc1 with commit f056fc2b927448d37eca6b6cacc3d1b0f67b20d2

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-2026-64255
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/agg.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/1de92789ce31e46fa7e7d8e89c90b19cdb1c103b
	https://git.kernel.org/stable/c/fe7f339f63c9dc4ca546ed7ac38ba4bb3a99dcfc
	https://git.kernel.org/stable/c/f056fc2b927448d37eca6b6cacc3d1b0f67b20d2