cfg80211: validate channel settings across interfaces

Currently, there's a problem that affects regulatory
enforcement and connection stability, in that it is
possible to switch the channel while connected to a
network or joined to an IBSS.

The problem comes from the fact that we only validate
the channel against the current interface's type, not
against any other interface. Thus, you have any type
of interface up, additionally bring up a monitor mode
interface and switch the channel on the monitor. This
will obviously also switch the channel on the other
interface.

The problem now is that if you do that while sending
beacons for IBSS mode, you can switch to a disabled
channel or a channel that doesn't allow beaconing.
Combined with a managed mode interface connected to
an AP instead of an IBSS interface, you can easily
break the connection that way.

To fix this, this patch validates any channel change
with all available interfaces, and disallows such
changes on secondary interfaces if another interface
is connected to an AP or joined to an IBSS.

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

1 files changed, 19 insertions, 36 deletions

diff --git a/net/wireless/wext-compat.c b/net/wireless/wext-compat.c
index e4e90e2..17648dc 100644
--- a/net/wireless/wext-compat.c
+++ b/net/wireless/wext-compat.c
@@ -267,39 +267,26 @@ EXPORT_SYMBOL_GPL(cfg80211_wext_giwrange);
  * @wiphy: the wiphy
  * @freq: the wext freq encoding
  *
- * Returns a channel, %NULL for auto, or an ERR_PTR for errors!
+ * Returns a frequency, or a negative error code, or 0 for auto.
  */
-struct ieee80211_channel *cfg80211_wext_freq(struct wiphy *wiphy,
-					     struct iw_freq *freq)
+int cfg80211_wext_freq(struct wiphy *wiphy, struct iw_freq *freq)
 {
-	struct ieee80211_channel *chan;
-	int f;
-
 	/*
-	 * Parse frequency - return NULL for auto and
+	 * Parse frequency - return 0 for auto and
 	 * -EINVAL for impossible things.
 	 */
 	if (freq->e == 0) {
 		if (freq->m < 0)
-			return NULL;
-		f = ieee80211_channel_to_frequency(freq->m);
+			return 0;
+		return ieee80211_channel_to_frequency(freq->m);
 	} else {
 		int i, div = 1000000;
 		for (i = 0; i < freq->e; i++)
 			div /= 10;
 		if (div <= 0)
-			return ERR_PTR(-EINVAL);
-		f = freq->m / div;
+			return -EINVAL;
+		return freq->m / div;
 	}
-
-	/*
-	 * Look up channel struct and return -EINVAL when
-	 * it cannot be found.
-	 */
-	chan = ieee80211_get_channel(wiphy, f);
-	if (!chan)
-		return ERR_PTR(-EINVAL);
-	return chan;
 }
 
 int cfg80211_wext_siwrts(struct net_device *dev,
@@ -761,33 +748,29 @@ EXPORT_SYMBOL_GPL(cfg80211_wext_giwencode);
 
 int cfg80211_wext_siwfreq(struct net_device *dev,
 			  struct iw_request_info *info,
-			  struct iw_freq *freq, char *extra)
+			  struct iw_freq *wextfreq, char *extra)
 {
 	struct wireless_dev *wdev = dev->ieee80211_ptr;
 	struct cfg80211_registered_device *rdev = wiphy_to_dev(wdev->wiphy);
-	struct ieee80211_channel *chan;
-	int err;
+	int freq, err;
 
 	switch (wdev->iftype) {
 	case NL80211_IFTYPE_STATION:
-		return cfg80211_mgd_wext_siwfreq(dev, info, freq, extra);
+		return cfg80211_mgd_wext_siwfreq(dev, info, wextfreq, extra);
 	case NL80211_IFTYPE_ADHOC:
-		return cfg80211_ibss_wext_siwfreq(dev, info, freq, extra);
+		return cfg80211_ibss_wext_siwfreq(dev, info, wextfreq, extra);
 	default:
-		chan = cfg80211_wext_freq(wdev->wiphy, freq);
-		if (!chan)
+		freq = cfg80211_wext_freq(wdev->wiphy, wextfreq);
+		if (freq < 0)
+			return freq;
+		if (freq == 0)
 			return -EINVAL;
-		if (IS_ERR(chan))
-			return PTR_ERR(chan);
-		err = rdev->ops->set_channel(wdev->wiphy, chan,
-					     NL80211_CHAN_NO_HT);
-		if (err)
-			return err;
-		rdev->channel = chan;
-		return 0;
+		mutex_lock(&rdev->devlist_mtx);
+		err = rdev_set_freq(rdev, freq, NL80211_CHAN_NO_HT);
+		mutex_unlock(&rdev->devlist_mtx);
+		return err;
 	}
 }
-EXPORT_SYMBOL_GPL(cfg80211_wext_siwfreq);
 
 int cfg80211_wext_giwfreq(struct net_device *dev,
 			  struct iw_request_info *info,