Re: [PATCH wireless] wifi: mt76: do not run mt76_unregister_device() on unregistered hw

[Lorenzo Bianconi <lorenzo@kernel.org>]

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> Trying to probe a mt7921e pci card without firmware results in a
> successful probe where ieee80211_register_hw hasn't been called. When
> removing the driver, ieee802111_unregister_hw is called unconditionally
> leading to a kernel NULL pointer dereference.
> Fix the issue running mt76_unregister_device routine just for registered
> hw.

Reviewing the code better, mt7921 is the only driver registering ieee80211_hw in
init work. I do not have a strong opinion if it is better this approach or the
fix posted by Helmut, I am fine both ways.

@Felix: what do you think?

Regards,
Lorenzo

> 
> Link: https://bugs.debian.org/1029116
> Link: https://bugs.kali.org/view.php?id=8140
> Reported-by: Stuart Hayhurst <stuart.a.hayhurst@gmail.com>
> Fixes: 1c71e03afe4b ("mt76: mt7921: move mt7921_init_hw in a dedicated work")
> Tested-by: Helmut Grohne <helmut@freexian.com>
> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> ---
>  drivers/net/wireless/mediatek/mt76/mac80211.c | 8 ++++++++
>  drivers/net/wireless/mediatek/mt76/mt76.h     | 1 +
>  2 files changed, 9 insertions(+)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mac80211.c b/drivers/net/wireless/mediatek/mt76/mac80211.c
> index b117e4467c87..34abf70f44af 100644
> --- a/drivers/net/wireless/mediatek/mt76/mac80211.c
> +++ b/drivers/net/wireless/mediatek/mt76/mac80211.c
> @@ -539,6 +539,7 @@ int mt76_register_phy(struct mt76_phy *phy, bool vht,
>  	if (ret)
>  		return ret;
>  
> +	set_bit(MT76_STATE_REGISTERED, &phy->state);
>  	phy->dev->phys[phy->band_idx] = phy;
>  
>  	return 0;
> @@ -549,6 +550,9 @@ void mt76_unregister_phy(struct mt76_phy *phy)
>  {
>  	struct mt76_dev *dev = phy->dev;
>  
> +	if (!test_bit(MT76_STATE_REGISTERED, &phy->state))
> +		return;
> +
>  	if (IS_ENABLED(CONFIG_MT76_LEDS))
>  		mt76_led_cleanup(phy);
>  	mt76_tx_status_check(dev, true);
> @@ -719,6 +723,7 @@ int mt76_register_device(struct mt76_dev *dev, bool vht,
>  		return ret;
>  
>  	WARN_ON(mt76_worker_setup(hw, &dev->tx_worker, NULL, "tx"));
> +	set_bit(MT76_STATE_REGISTERED, &phy->state);
>  	sched_set_fifo_low(dev->tx_worker.task);
>  
>  	return 0;
> @@ -729,6 +734,9 @@ void mt76_unregister_device(struct mt76_dev *dev)
>  {
>  	struct ieee80211_hw *hw = dev->hw;
>  
> +	if (!test_bit(MT76_STATE_REGISTERED, &dev->phy.state))
> +		return;
> +
>  	if (IS_ENABLED(CONFIG_MT76_LEDS))
>  		mt76_led_cleanup(&dev->phy);
>  	mt76_tx_status_check(dev, true);
> diff --git a/drivers/net/wireless/mediatek/mt76/mt76.h b/drivers/net/wireless/mediatek/mt76/mt76.h
> index ccca0162c8f8..183b0fc5a2d4 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt76.h
> +++ b/drivers/net/wireless/mediatek/mt76/mt76.h
> @@ -402,6 +402,7 @@ struct mt76_tx_cb {
>  
>  enum {
>  	MT76_STATE_INITIALIZED,
> +	MT76_STATE_REGISTERED,
>  	MT76_STATE_RUNNING,
>  	MT76_STATE_MCU_RUNNING,
>  	MT76_SCANNING,
> -- 
> 2.39.2
> 

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