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, 1 insertions, 2 deletions

diff --git a/net/wireless/wext-compat.h b/net/wireless/wext-compat.h
index 9a37747..20b3dae 100644
--- a/net/wireless/wext-compat.h
+++ b/net/wireless/wext-compat.h
@@ -42,8 +42,7 @@ int cfg80211_mgd_wext_giwessid(struct net_device *dev,
 			       struct iw_request_info *info,
 			       struct iw_point *data, char *ssid);
 
-struct ieee80211_channel *cfg80211_wext_freq(struct wiphy *wiphy,
-					     struct iw_freq *freq);
+int cfg80211_wext_freq(struct wiphy *wiphy, struct iw_freq *freq);
 
 
 extern const struct iw_handler_def cfg80211_wext_handler;