Subject: CVE-2022-48808: net: dsa: fix panic when DSA master device unbinds on shutdown

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

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

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

net: dsa: fix panic when DSA master device unbinds on shutdown

Rafael reports that on a system with LX2160A and Marvell DSA switches,
if a reboot occurs while the DSA master (dpaa2-eth) is up, the following
panic can be seen:

systemd-shutdown[1]: Rebooting.
Unable to handle kernel paging request at virtual address 00a0000800000041
[00a0000800000041] address between user and kernel address ranges
Internal error: Oops: 96000004 [#1] PREEMPT SMP
CPU: 6 PID: 1 Comm: systemd-shutdow Not tainted 5.16.5-00042-g8f5585009b24 #32
pc : dsa_slave_netdevice_event+0x130/0x3e4
lr : raw_notifier_call_chain+0x50/0x6c
Call trace:
 dsa_slave_netdevice_event+0x130/0x3e4
 raw_notifier_call_chain+0x50/0x6c
 call_netdevice_notifiers_info+0x54/0xa0
 __dev_close_many+0x50/0x130
 dev_close_many+0x84/0x120
 unregister_netdevice_many+0x130/0x710
 unregister_netdevice_queue+0x8c/0xd0
 unregister_netdev+0x20/0x30
 dpaa2_eth_remove+0x68/0x190
 fsl_mc_driver_remove+0x20/0x5c
 __device_release_driver+0x21c/0x220
 device_release_driver_internal+0xac/0xb0
 device_links_unbind_consumers+0xd4/0x100
 __device_release_driver+0x94/0x220
 device_release_driver+0x28/0x40
 bus_remove_device+0x118/0x124
 device_del+0x174/0x420
 fsl_mc_device_remove+0x24/0x40
 __fsl_mc_device_remove+0xc/0x20
 device_for_each_child+0x58/0xa0
 dprc_remove+0x90/0xb0
 fsl_mc_driver_remove+0x20/0x5c
 __device_release_driver+0x21c/0x220
 device_release_driver+0x28/0x40
 bus_remove_device+0x118/0x124
 device_del+0x174/0x420
 fsl_mc_bus_remove+0x80/0x100
 fsl_mc_bus_shutdown+0xc/0x1c
 platform_shutdown+0x20/0x30
 device_shutdown+0x154/0x330
 __do_sys_reboot+0x1cc/0x250
 __arm64_sys_reboot+0x20/0x30
 invoke_syscall.constprop.0+0x4c/0xe0
 do_el0_svc+0x4c/0x150
 el0_svc+0x24/0xb0
 el0t_64_sync_handler+0xa8/0xb0
 el0t_64_sync+0x178/0x17c

It can be seen from the stack trace that the problem is that the
deregistration of the master causes a dev_close(), which gets notified
as NETDEV_GOING_DOWN to dsa_slave_netdevice_event().
But dsa_switch_shutdown() has already run, and this has unregistered the
DSA slave interfaces, and yet, the NETDEV_GOING_DOWN handler attempts to
call dev_close_many() on those slave interfaces, leading to the problem.

The previous attempt to avoid the NETDEV_GOING_DOWN on the master after
dsa_switch_shutdown() was called seems improper. Unregistering the slave
interfaces is unnecessary and unhelpful. Instead, after the slaves have
stopped being uppers of the DSA master, we can now reset to NULL the
master->dsa_ptr pointer, which will make DSA start ignoring all future
notifier events on the master.

The Linux kernel CVE team has assigned CVE-2022-48808 to this issue.

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

	Issue introduced in 5.15 with commit 0650bf52b31f and fixed in 5.15.155 with commit ff45899e732e
	Issue introduced in 5.15 with commit 0650bf52b31f and fixed in 5.16.10 with commit 89b60402d43c
	Issue introduced in 5.15 with commit 0650bf52b31f and fixed in 5.17 with commit ee534378f005

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-2022-48808
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/dsa/dsa2.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/ff45899e732e57088985e3a497b1d9100571c0f5
	https://git.kernel.org/stable/c/89b60402d43cdab4387dbbf24afebda5cf092ae7
	https://git.kernel.org/stable/c/ee534378f00561207656663d93907583958339ae