Re: [PATCH] wifi: mt76: mt7921: correctly handle removal in the absence of firmware

[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 among other things.
> 
> As with other drivers that delay registration after probe, we track the
> registration state in a flag variable and conidtionalize deregistration.
> 
> 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")
> Signed-off-by: Helmut Grohne <helmut@freexian.com>
> Cc: stable@vger.kernel.org
> Sponsored-by: Freexian and Offensive Security

Hi Helmut,

Thx for working on this. I would say it is a more general issue since we have
dbdc support in mt7915/mt7996/mt7915 devices. I think we can move the check in
mac80211.c, what do you think? Something like (please note this patch is not
tested):

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 4ffb6be63571..38c311760d15 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,

Regards,
Lorenzo

> ---
>  drivers/net/wireless/mediatek/mt76/mt7921/init.c   | 1 +
>  drivers/net/wireless/mediatek/mt76/mt7921/mt7921.h | 1 +
>  drivers/net/wireless/mediatek/mt76/mt7921/pci.c    | 3 ++-
>  drivers/net/wireless/mediatek/mt76/mt7921/sdio.c   | 3 ++-
>  drivers/net/wireless/mediatek/mt76/mt7921/usb.c    | 3 ++-
>  5 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/init.c b/drivers/net/wireless/mediatek/mt76/mt7921/init.c
> index 542dfd425129..d5438212d5ff 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7921/init.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt7921/init.c
> @@ -315,6 +315,7 @@ static void mt7921_init_work(struct work_struct *work)
>  		dev_err(dev->mt76.dev, "register device failed\n");
>  		return;
>  	}
> +	dev->hw_registered = true;
>  
>  	ret = mt7921_init_debugfs(dev);
>  	if (ret) {
> diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/mt7921.h b/drivers/net/wireless/mediatek/mt76/mt7921/mt7921.h
> index 15d6b7fe1c6c..e3b5d8ebf243 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7921/mt7921.h
> +++ b/drivers/net/wireless/mediatek/mt76/mt7921/mt7921.h
> @@ -288,6 +288,7 @@ struct mt7921_dev {
>  	bool hw_full_reset:1;
>  	bool hw_init_done:1;
>  	bool fw_assert:1;
> +	bool hw_registered:1;
>  
>  	struct list_head sta_poll_list;
>  	spinlock_t sta_poll_lock;
> diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/pci.c b/drivers/net/wireless/mediatek/mt76/mt7921/pci.c
> index cb72ded37256..1841eb7345dc 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7921/pci.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt7921/pci.c
> @@ -110,7 +110,8 @@ static void mt7921e_unregister_device(struct mt7921_dev *dev)
>  	struct mt76_connac_pm *pm = &dev->pm;
>  
>  	cancel_work_sync(&dev->init_work);
> -	mt76_unregister_device(&dev->mt76);
> +	if (dev->hw_registered)
> +		mt76_unregister_device(&dev->mt76);
>  	mt76_for_each_q_rx(&dev->mt76, i)
>  		napi_disable(&dev->mt76.napi[i]);
>  	cancel_delayed_work_sync(&pm->ps_work);
> diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/sdio.c b/drivers/net/wireless/mediatek/mt76/mt7921/sdio.c
> index 8ce4252b8ae7..23a9dd3c6450 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7921/sdio.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt7921/sdio.c
> @@ -43,7 +43,8 @@ static void mt7921s_unregister_device(struct mt7921_dev *dev)
>  	struct mt76_connac_pm *pm = &dev->pm;
>  
>  	cancel_work_sync(&dev->init_work);
> -	mt76_unregister_device(&dev->mt76);
> +	if (dev->hw_registered)
> +		mt76_unregister_device(&dev->mt76);
>  	cancel_delayed_work_sync(&pm->ps_work);
>  	cancel_work_sync(&pm->wake_work);
>  
> diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/usb.c b/drivers/net/wireless/mediatek/mt76/mt7921/usb.c
> index 5321d20dcdcb..e55e1b50f760 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7921/usb.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt7921/usb.c
> @@ -301,7 +301,8 @@ static void mt7921u_disconnect(struct usb_interface *usb_intf)
>  	if (!test_bit(MT76_STATE_INITIALIZED, &dev->mphy.state))
>  		return;
>  
> -	mt76_unregister_device(&dev->mt76);
> +	if (dev->hw_registered)
> +		mt76_unregister_device(&dev->mt76);
>  	mt7921u_cleanup(dev);
>  
>  	usb_set_intfdata(usb_intf, NULL);
> -- 
> 2.39.0
> 
> 

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