CVE-2021-47349

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]