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, 9 insertions, 0 deletions

diff --git a/net/wireless/sme.c b/net/wireless/sme.c
index 340934f..219c3bc 100644
--- a/net/wireless/sme.c
+++ b/net/wireless/sme.c
@@ -256,9 +256,11 @@ void cfg80211_sme_scan_done(struct net_device *dev)
 {
 	struct wireless_dev *wdev = dev->ieee80211_ptr;
 
+	mutex_lock(&wiphy_to_dev(wdev->wiphy)->devlist_mtx);
 	wdev_lock(wdev);
 	__cfg80211_sme_scan_done(dev);
 	wdev_unlock(wdev);
+	mutex_unlock(&wiphy_to_dev(wdev->wiphy)->devlist_mtx);
 }
 
 void cfg80211_sme_rx_auth(struct net_device *dev,
@@ -644,6 +646,7 @@ int __cfg80211_connect(struct cfg80211_registered_device *rdev,
 		       struct cfg80211_cached_keys *connkeys)
 {
 	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct ieee80211_channel *chan;
 	int err;
 
 	ASSERT_WDEV_LOCK(wdev);
@@ -651,6 +654,10 @@ int __cfg80211_connect(struct cfg80211_registered_device *rdev,
 	if (wdev->sme_state != CFG80211_SME_IDLE)
 		return -EALREADY;
 
+	chan = rdev_fixed_channel(rdev, wdev);
+	if (chan && chan != connect->channel)
+		return -EBUSY;
+
 	if (WARN_ON(wdev->connect_keys)) {
 		kfree(wdev->connect_keys);
 		wdev->connect_keys = NULL;
@@ -785,9 +792,11 @@ int cfg80211_connect(struct cfg80211_registered_device *rdev,
 {
 	int err;
 
+	mutex_lock(&rdev->devlist_mtx);
 	wdev_lock(dev->ieee80211_ptr);
 	err = __cfg80211_connect(rdev, dev, connect, connkeys);
 	wdev_unlock(dev->ieee80211_ptr);
+	mutex_unlock(&rdev->devlist_mtx);
 
 	return err;
 }