Brian Norris <briannorris@xxxxxxxxxxxx> wrote:
> 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]
>
> Fixes: a05829a7222e ("cfg80211: avoid holding the RTNL when calling the driver")
> Cc: stable@xxxxxxxxxxxxxxx
> Link: https://lore.kernel.org/linux-wireless/98392296-40ee-6300-369c-32e16cff3725@xxxxxxxxx/
> Link: https://lore.kernel.org/linux-wireless/ab4d00ce52f32bd8e45ad0448a44737e@xxxxxxxxx/
> Reported-by: Maximilian Luz <luzmaximilian@xxxxxxxxx>
> Reported-by: dave@xxxxxxxxx
> Cc: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
> Signed-off-by: Brian Norris <briannorris@xxxxxxxxxxxx>
> Tested-by: Maximilian Luz <luzmaximilian@xxxxxxxxx>
> Tested-by: Dave Olsthoorn <dave@xxxxxxxxx>
Patch applied to wireless-drivers.git, thanks.
1f9482aa8d41 mwifiex: bring down link before deleting interface
--
https://patchwork.kernel.org/project/linux-wireless/patch/20210515024227.2159311-1-briannorris@xxxxxxxxxxxx/
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
