iwlwifi: do not nulify ctx->vif on reset

ctx->vif is dereferenced in different part of iwlwifi code, so do not
nullify it.

This should address at least one of the possible reasons of WARNING at
iwlagn_mac_remove_interface, and perhaps some random crashes when
firmware reset is performed.

Cc: stable@vger.kernel.org
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn.c

@@ -863,7 +863,6 @@ static void iwl_bg_run_time_calib_work(struct work_struct *work)
 
 void iwlagn_prepare_restart(struct iwl_priv *priv)
 {
-	struct iwl_rxon_context *ctx;
 	bool bt_full_concurrent;
 	u8 bt_ci_compliance;
 	u8 bt_load;
@@ -872,8 +871,6 @@ void iwlagn_prepare_restart(struct iwl_priv *priv)
 
 	lockdep_assert_held(&priv->mutex);
 
-	for_each_context(priv, ctx)
-		ctx->vif = NULL;
 	priv->is_open = 0;
 
 	/*

drivers/net/wireless/iwlwifi/iwl-mac80211.c

@@ -1244,6 +1244,7 @@ static int iwlagn_mac_add_interface(struct ieee80211_hw *hw,
 	struct iwl_rxon_context *tmp, *ctx = NULL;
 	int err;
 	enum nl80211_iftype viftype = ieee80211_vif_type_p2p(vif);
+	bool reset = false;
 
 	IWL_DEBUG_MAC80211(priv, "enter: type %d, addr %pM\n",
 			   viftype, vif->addr);
@@ -1265,6 +1266,13 @@ static int iwlagn_mac_add_interface(struct ieee80211_hw *hw,
 			tmp->interface_modes | tmp->exclusive_interface_modes;
 
 		if (tmp->vif) {
+			/* On reset we need to add the same interface again */
+			if (tmp->vif == vif) {
+				reset = true;
+				ctx = tmp;
+				break;
+			}
+
 			/* check if this busy context is exclusive */
 			if (tmp->exclusive_interface_modes &
 						BIT(tmp->vif->type)) {
@@ -1291,7 +1299,7 @@ static int iwlagn_mac_add_interface(struct ieee80211_hw *hw,
 	ctx->vif = vif;
 
 	err = iwl_setup_interface(priv, ctx);
-	if (!err)
+	if (!err || reset)
 		goto out;
 
 	ctx->vif = NULL;