cfg80211: refuse to .set_monitor_channel when non-monitors are present

Having .set_monitor_channel work with non-monitor
interfaces running would make interface
combinations accounting ambiguous.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/wireless/chan.c b/net/wireless/chan.c
index 167e7cb60089..019401b0b5e3 100644
--- a/net/wireless/chan.c
+++ b/net/wireless/chan.c
@@ -85,6 +85,8 @@ int cfg80211_set_monitor_channel(struct cfg80211_registered_device *rdev,
 
         if (!rdev->ops->set_monitor_channel)
                 return -EOPNOTSUPP;
+        if (!cfg80211_has_monitors_only(rdev))
+                return -EBUSY;
 
         chan = rdev_freq_to_chan(rdev, freq, chantype);
         if (!chan)