CVE-2026-68332: net: airoha: Fix potential use-after-free in airoha_ppe_deinit()

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

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

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

net: airoha: Fix potential use-after-free in airoha_ppe_deinit()

airoha_ppe_deinit() replaces the NPU pointer with NULL via
rcu_replace_pointer() but does not wait for existing RCU readers
to exit before calling ppe_deinit() and airoha_npu_put(). This can
cause a use-after-free if a reader in an RCU read-side critical
section still holds a reference to the NPU when it is freed.

The init path (airoha_ppe_init) already calls synchronize_rcu()
after rcu_assign_pointer(), but the deinit path introduced in
commit 6abcf751bc08 ("net: airoha: Fix schedule while atomic in
airoha_ppe_deinit()") omitted the matching barrier when switching
from rcu_read_lock()/rcu_dereference() to rcu_replace_pointer().

Add synchronize_rcu() before ppe_deinit() to ensure all existing
RCU readers have completed before the NPU resources are released.

The Linux kernel CVE team has assigned CVE-2026-68332 to this issue.


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

	Issue introduced in 6.18.6 with commit 72f93dc6d1a6b157e0c3d247085c74935893cca0 and fixed in 6.18.42 with commit 46e3bed4b071095ecc9384a7b349e1908728531f
	Issue introduced in 6.19 with commit 6abcf751bc084804a9e5b3051442e8a2ce67f48a and fixed in 7.1.6 with commit ad28c4f9e0eae4993cb3fde3e7cea330acd8b97c
	Issue introduced in 6.19 with commit 6abcf751bc084804a9e5b3051442e8a2ce67f48a and fixed in 7.2-rc5 with commit 2484568a335cd7bda951c75b3a7d95ea36161ae7

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-2026-68332
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/ethernet/airoha/airoha_ppe.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/46e3bed4b071095ecc9384a7b349e1908728531f
	https://git.kernel.org/stable/c/ad28c4f9e0eae4993cb3fde3e7cea330acd8b97c
	https://git.kernel.org/stable/c/2484568a335cd7bda951c75b3a7d95ea36161ae7