mac80211: fix ibss scanning

Do not scan on no-IBSS and disabled channels in IBSS mode. Doing this
can trigger Microcode errors on iwlwifi and iwlegacy drivers.

Also rename ieee80211_request_internal_scan() function since it is only
used in IBSS mode and simplify calling it from ieee80211_sta_find_ibss().

This patch should address:
https://bugzilla.redhat.com/show_bug.cgi?id=883414
https://bugzilla.kernel.org/show_bug.cgi?id=49411

Reported-by: Jesse Kahtava <jesse_kahtava@f-m.fm>
Reported-by: Mikko Rapeli  <mikko.rapeli@iki.fi>
Cc: stable@vger.kernel.org
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 8ed83dc..de3532d 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -832,9 +832,9 @@
 	return res;
 }
 
-int ieee80211_request_internal_scan(struct ieee80211_sub_if_data *sdata,
-				    const u8 *ssid, u8 ssid_len,
-				    struct ieee80211_channel *chan)
+int ieee80211_request_ibss_scan(struct ieee80211_sub_if_data *sdata,
+				const u8 *ssid, u8 ssid_len,
+				struct ieee80211_channel *chan)
 {
 	struct ieee80211_local *local = sdata->local;
 	int ret = -EBUSY;
@@ -848,22 +848,36 @@
 
 	/* fill internal scan request */
 	if (!chan) {
-		int i, nchan = 0;
+		int i, max_n;
+		int n_ch = 0;
 
 		for (band = 0; band < IEEE80211_NUM_BANDS; band++) {
 			if (!local->hw.wiphy->bands[band])
 				continue;
-			for (i = 0;
-			     i < local->hw.wiphy->bands[band]->n_channels;
-			     i++) {
-				local->int_scan_req->channels[nchan] =
+
+			max_n = local->hw.wiphy->bands[band]->n_channels;
+			for (i = 0; i < max_n; i++) {
+				struct ieee80211_channel *tmp_ch =
 				    &local->hw.wiphy->bands[band]->channels[i];
-				nchan++;
+
+				if (tmp_ch->flags & (IEEE80211_CHAN_NO_IBSS |
+						     IEEE80211_CHAN_DISABLED))
+					continue;
+
+				local->int_scan_req->channels[n_ch] = tmp_ch;
+				n_ch++;
 			}
 		}
 
-		local->int_scan_req->n_channels = nchan;
+		if (WARN_ON_ONCE(n_ch == 0))
+			goto unlock;
+
+		local->int_scan_req->n_channels = n_ch;
 	} else {
+		if (WARN_ON_ONCE(chan->flags & (IEEE80211_CHAN_NO_IBSS |
+						IEEE80211_CHAN_DISABLED)))
+			goto unlock;
+
 		local->int_scan_req->channels[0] = chan;
 		local->int_scan_req->n_channels = 1;
 	}