wifi: cfg80211: clear link ID from bitmap during link delete after clean up

Currently, during link deletion, the link ID is first removed from the
valid_links bitmap before performing any clean-up operations. However, some
functions require the link ID to remain in the valid_links bitmap. One
such example is cfg80211_cac_event(). The flow is -

nl80211_remove_link()
    cfg80211_remove_link()
        ieee80211_del_intf_link()
            ieee80211_vif_set_links()
                ieee80211_vif_update_links()
                    ieee80211_link_stop()
                        cfg80211_cac_event()

cfg80211_cac_event() requires link ID to be present but it is cleared
already in cfg80211_remove_link(). Ultimately, WARN_ON() is hit.

Therefore, clear the link ID from the bitmap only after completing the link
clean-up.

Signed-off-by: Aditya Kumar Singh <quic_adisi@quicinc.com>
Link: https://patch.msgid.link/20241121-mlo_dfs_fix-v2-1-92c3bf7ab551@quicinc.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Author: Aditya Kumar Singh

net/mac80211/cfg.c

@@ -5046,10 +5046,16 @@ static void ieee80211_del_intf_link(struct wiphy *wiphy,
 				    unsigned int link_id)
 {
 	struct ieee80211_sub_if_data *sdata = IEEE80211_WDEV_TO_SUB_IF(wdev);
+	u16 new_links = wdev->valid_links & ~BIT(link_id);
 
 	lockdep_assert_wiphy(sdata->local->hw.wiphy);
 
-	ieee80211_vif_set_links(sdata, wdev->valid_links, 0);
+	/* During the link teardown process, certain functions require the
+	 * link_id to remain in the valid_links bitmap. Therefore, instead
+	 * of removing the link_id from the bitmap, pass a masked value to
+	 * simulate as if link_id does not exist anymore.
+	 */
+	ieee80211_vif_set_links(sdata, new_links, 0);
 }
 
 static int

net/wireless/util.c

@@ -2843,10 +2843,9 @@ void cfg80211_remove_link(struct wireless_dev *wdev, unsigned int link_id)
 		break;
 	}
 
-	wdev->valid_links &= ~BIT(link_id);
-
 	rdev_del_intf_link(rdev, wdev, link_id);
 
+	wdev->valid_links &= ~BIT(link_id);
 	eth_zero_addr(wdev->links[link_id].addr);
 }