CVE-2026-98708: wifi: mac80211: keep paired old chanctx alive

CVE-2026-98708: wifi: mac80211: keep paired old chanctx alive

[Greg Kroah-Hartman]

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

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

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

wifi: mac80211: keep paired old chanctx alive

An in-place replacement keeps reciprocal replace_ctx pointers between
the old WILL_BE_REPLACED chanctx and the new REPLACES_OTHER chanctx.
However, the early free paths only consider assigned and reserved link
users when deciding whether to free the old chanctx.

That lets the old chanctx be freed too early while the replacement
partner still points back to it, either when the last assigned link is
released or when that link successfully reassigns to another existing
context. Later unreserve and switch-finalization paths can then follow a
stale replace_ctx pointer.

Keep a paired old chanctx alive until the replacement pair has been torn
down. Apply the same check to both __ieee80211_link_release_channel()
and ieee80211_link_use_reserved_reassign(). If the replacement is later
abandoned, ieee80211_link_unreserve_chanctx() already tears down the
pairing before freeing the old chanctx once no users remain.

The Linux kernel CVE team has assigned CVE-2026-98708 to this issue.


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

	Issue introduced in 3.17 with commit 5bcae31d9cb1ebfad3ad5a3eea04c8cdc329a04f and fixed in 6.12.113 with commit 21a688cbeae0e682f03e91f1e7a7eedd60d9d4f2
	Issue introduced in 3.17 with commit 5bcae31d9cb1ebfad3ad5a3eea04c8cdc329a04f and fixed in 6.18.56 with commit 1c82d0c5d509179ba2a4edfa096f516aebf960b0
	Issue introduced in 3.17 with commit 5bcae31d9cb1ebfad3ad5a3eea04c8cdc329a04f and fixed in 7.2.10 with commit afd1cdd16a25c7185b812a612ab7d5f2cbd1e086
	Issue introduced in 3.17 with commit 5bcae31d9cb1ebfad3ad5a3eea04c8cdc329a04f and fixed in 7.3-rc6 with commit 3412e9a800786d1dec4a58367db1cba275e7ef11

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-2026-98708
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/mac80211/chan.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/21a688cbeae0e682f03e91f1e7a7eedd60d9d4f2
	https://git.kernel.org/stable/c/1c82d0c5d509179ba2a4edfa096f516aebf960b0
	https://git.kernel.org/stable/c/afd1cdd16a25c7185b812a612ab7d5f2cbd1e086
	https://git.kernel.org/stable/c/3412e9a800786d1dec4a58367db1cba275e7ef11