cfg80211: fix locking

Over time, a lot of locking issues have crept into
the smarts of cfg80211, so e.g. scan completion can
race against a new scan, IBSS join can race against
leaving an IBSS, etc.

Introduce a new per-interface lock that protects
most of the per-interface data that we need to keep
track of, and sprinkle assertions about that lock
everywhere. Some things now need to be offloaded to
work structs so that we don't require being able to
sleep in functions the drivers call. The exception
to that are the MLME callbacks (rx_auth etc.) that
currently only mac80211 calls because it was easier
to do that there instead of in cfg80211, and future
drivers implementing those calls will, if they ever
exist, probably need to use a similar scheme like
mac80211 anyway...

In order to be able to handle _deauth and _disassoc
properly, introduce a cookie passed to it that will
determine locking requirements.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/wireless/nl80211.c

@@ -4029,6 +4029,8 @@ static int nl80211_add_scan_req(struct sk_buff *msg,
 	struct nlattr *nest;
 	int i;
 
+	ASSERT_RDEV_LOCK(rdev);
+
 	if (WARN_ON(!req))
 		return 0;
 
@@ -4391,12 +4393,12 @@ void nl80211_send_roamed(struct cfg80211_registered_device *rdev,
 
 void nl80211_send_disconnected(struct cfg80211_registered_device *rdev,
 			       struct net_device *netdev, u16 reason,
-			       u8 *ie, size_t ie_len, bool from_ap, gfp_t gfp)
+			       const u8 *ie, size_t ie_len, bool from_ap)
 {
 	struct sk_buff *msg;
 	void *hdr;
 
-	msg = nlmsg_new(NLMSG_GOODSIZE, gfp);
+	msg = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
 	if (!msg)
 		return;
 
@@ -4420,7 +4422,7 @@ void nl80211_send_disconnected(struct cfg80211_registered_device *rdev,
 		return;
 	}
 
-	genlmsg_multicast(msg, 0, nl80211_mlme_mcgrp.id, gfp);
+	genlmsg_multicast(msg, 0, nl80211_mlme_mcgrp.id, GFP_KERNEL);
 	return;
 
  nla_put_failure: