iwlegacy: fix bugs in change_interface

If change_interface gets invoked during a firmware
restart, it may crash; prevent that from happening
by checking if ctx->vif is assigned.

Additionally, in my initial commit I forgot to set
the vif->p2p variable correctly, so fix that too.

Cc: stable@kernel.org [2.6.38+]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlegacy/iwl-core.c

@@ -1805,6 +1805,15 @@ iwl_legacy_mac_change_interface(struct ieee80211_hw *hw,
 
 	mutex_lock(&priv->mutex);
 
+	if (!ctx->vif || !iwl_legacy_is_ready_rf(priv)) {
+		/*
+		 * Huh? But wait ... this can maybe happen when
+		 * we're in the middle of a firmware restart!
+		 */
+		err = -EBUSY;
+		goto out;
+	}
+
 	interface_modes = ctx->interface_modes | ctx->exclusive_interface_modes;
 
 	if (!(interface_modes & BIT(newtype))) {
@@ -1832,6 +1841,7 @@ iwl_legacy_mac_change_interface(struct ieee80211_hw *hw,
 	/* success */
 	iwl_legacy_teardown_interface(priv, vif, true);
 	vif->type = newtype;
+	vif->p2p = newp2p;
 	err = iwl_legacy_setup_interface(priv, ctx);
 	WARN_ON(err);
 	/*