wifi: mt76: scan: Fix 'mlink' dereferenced before IS_ERR_OR_NULL check

JIRA: https://issues.redhat.com/browse/RHEL-89168

commit 7e1fcf6
Author: Feng Jiang <jiangfeng@kylinos.cn>
Date:   Wed Apr 2 14:24:15 2025 +0800

    wifi: mt76: scan: Fix 'mlink' dereferenced before IS_ERR_OR_NULL check
    
    Reported-by: kernel test robot <lkp@intel.com>
    Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
    Closes: https://lore.kernel.org/r/202504011739.HvUKtUUe-lkp@intel.com/
    Fixes: 3ba20af ("wifi: mt76: scan: set vif offchannel link for scanning/roc")
    Signed-off-by: Feng Jiang <jiangfeng@kylinos.cn>
    Link: https://patch.msgid.link/20250402062415.25434-1-jiangfeng@kylinos.cn
    Signed-off-by: Felix Fietkau <nbd@nbd.name>

Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm@redhat.com>

Author: jtornosm

drivers/net/wireless/mediatek/mt76/channel.c

@@ -302,11 +302,13 @@ void mt76_put_vif_phy_link(struct mt76_phy *phy, struct ieee80211_vif *vif,
 			   struct mt76_vif_link *mlink)
 {
 	struct mt76_dev *dev = phy->dev;
-	struct mt76_vif_data *mvif = mlink->mvif;
+	struct mt76_vif_data *mvif;
 
 	if (IS_ERR_OR_NULL(mlink) || !mlink->offchannel)
 		return;
 
+	mvif = mlink->mvif;
+
 	rcu_assign_pointer(mvif->offchannel_link, NULL);
 	dev->drv->vif_link_remove(phy, vif, &vif->bss_conf, mlink);
 	kfree(mlink);