Subject: CVE-2021-47349: mwifiex: bring down link before deleting interface

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

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

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

mwifiex: bring down link before deleting interface

We can deadlock when rmmod'ing the driver or going through firmware
reset, because the cfg80211_unregister_wdev() has to bring down the link
for us, ... which then grab the same wiphy lock.

nl80211_del_interface() already handles a very similar case, with a nice
description:

        /*
         * We hold RTNL, so this is safe, without RTNL opencount cannot
         * reach 0, and thus the rdev cannot be deleted.
         *
         * We need to do it for the dev_close(), since that will call
         * the netdev notifiers, and we need to acquire the mutex there
         * but don't know if we get there from here or from some other
         * place (e.g. "ip link set ... down").
         */
        mutex_unlock(&rdev->wiphy.mtx);
...

Do similarly for mwifiex teardown, by ensuring we bring the link down
first.

Sample deadlock trace:

[  247.103516] INFO: task rmmod:2119 blocked for more than 123 seconds.
[  247.110630]       Not tainted 5.12.4 #5
[  247.115796] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  247.124557] task:rmmod           state:D stack:    0 pid: 2119 ppid:  2114 flags:0x00400208
[  247.133905] Call trace:
[  247.136644]  __switch_to+0x130/0x170
[  247.140643]  __schedule+0x714/0xa0c
[  247.144548]  schedule_preempt_disabled+0x88/0xf4
[  247.149714]  __mutex_lock_common+0x43c/0x750
[  247.154496]  mutex_lock_nested+0x5c/0x68
[  247.158884]  cfg80211_netdev_notifier_call+0x280/0x4e0 [cfg80211]
[  247.165769]  raw_notifier_call_chain+0x4c/0x78
[  247.170742]  call_netdevice_notifiers_info+0x68/0xa4
[  247.176305]  __dev_close_many+0x7c/0x138
[  247.180693]  dev_close_many+0x7c/0x10c
[  247.184893]  unregister_netdevice_many+0xfc/0x654
[  247.190158]  unregister_netdevice_queue+0xb4/0xe0
[  247.195424]  _cfg80211_unregister_wdev+0xa4/0x204 [cfg80211]
[  247.201816]  cfg80211_unregister_wdev+0x20/0x2c [cfg80211]
[  247.208016]  mwifiex_del_virtual_intf+0xc8/0x188 [mwifiex]
[  247.214174]  mwifiex_uninit_sw+0x158/0x1b0 [mwifiex]
[  247.219747]  mwifiex_remove_card+0x38/0xa0 [mwifiex]
[  247.225316]  mwifiex_pcie_remove+0xd0/0xe0 [mwifiex_pcie]
[  247.231451]  pci_device_remove+0x50/0xe0
[  247.235849]  device_release_driver_internal+0x110/0x1b0
[  247.241701]  driver_detach+0x5c/0x9c
[  247.245704]  bus_remove_driver+0x84/0xb8
[  247.250095]  driver_unregister+0x3c/0x60
[  247.254486]  pci_unregister_driver+0x2c/0x90
[  247.259267]  cleanup_module+0x18/0xcdc [mwifiex_pcie]

The Linux kernel CVE team has assigned CVE-2021-47349 to this issue.

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

	Issue introduced in 5.12 with commit a05829a7222e and fixed in 5.12.18 with commit a3041d39d3c1
	Issue introduced in 5.12 with commit a05829a7222e and fixed in 5.13.3 with commit 35af69c7c049
	Issue introduced in 5.12 with commit a05829a7222e and fixed in 5.14 with commit 1f9482aa8d41

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-2021-47349
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/marvell/mwifiex/main.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/a3041d39d3c14da97fa3476835aba043ba810cf0
	https://git.kernel.org/stable/c/35af69c7c0490fdccfc159c6a87e4d1dc070838a
	https://git.kernel.org/stable/c/1f9482aa8d412b4ba06ce6ab8e333fb8ca29a06e