mac80211: choose first enabled channel for monitor

[ Upstream commit 041c881a0ba8a75f71118bd9766b78f04beed469 ]

Even if the first channel from sband channel list is invalid
or disabled mac80211 ends up choosing it as the default channel
for monitor interfaces, making them not usable.

Fix this by assigning the first available valid or enabled
channel instead.

Signed-off-by: Karthikeyan Kathirvel <kathirve@codeaurora.org>
Link: https://lore.kernel.org/r/1615440547-7661-1-git-send-email-kathirve@codeaurora.org
[reword commit message, comment, code cleanups]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index e3bbfb20ae829ae80ecef5a3b1bca5458dde0522..f31fd21d59ba97ed0ddb995b99f618be82818b66 100644 (file)
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -906,8 +906,19 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
                        continue;
 
                if (!dflt_chandef.chan) {
+                       /*
+                        * Assign the first enabled channel to dflt_chandef
+                        * from the list of channels
+                        */
+                       for (i = 0; i < sband->n_channels; i++)
+                               if (!(sband->channels[i].flags &
+                                               IEEE80211_CHAN_DISABLED))
+                                       break;
+                       /* if none found then use the first anyway */
+                       if (i == sband->n_channels)
+                               i = 0;
                        cfg80211_chandef_create(&dflt_chandef,
-                                               &sband->channels[0],
+                                               &sband->channels[i],
                                                NL80211_CHAN_NO_HT);
                        /* init channel we're on */
                        if (!local->use_chanctx && !local->_oper_chandef.chan) {