This is a note to let you know that I've just added the patch titled cfg80211: correct bridge/4addr mode check to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: cfg80211-correct-bridge-4addr-mode-check.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 2ff2c6176c71e0d8101ee70fd6a45d5192c4761f Author: Janusz Dziedzic <janusz.dziedzic@xxxxxxxxx> Date: Sun Oct 24 22:15:46 2021 +0200 cfg80211: correct bridge/4addr mode check [ Upstream commit 689a0a9f505f7bffdefe6f17fddb41c8ab6344f6 ] Without the patch we fail: $ sudo brctl addbr br0 $ sudo brctl addif br0 wlp1s0 $ sudo iw wlp1s0 set 4addr on command failed: Device or resource busy (-16) Last command failed but iface was already in 4addr mode. Fixes: ad4bb6f8883a ("cfg80211: disallow bridging managed/adhoc interfaces") Signed-off-by: Janusz Dziedzic <janusz.dziedzic@xxxxxxxxx> Link: https://lore.kernel.org/r/20211024201546.614379-1-janusz.dziedzic@xxxxxxxxx [add fixes tag, fix indentation, edit commit log] Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/net/wireless/util.c b/net/wireless/util.c index 82b3baed2c7d..aaefaf3422a1 100644 --- a/net/wireless/util.c +++ b/net/wireless/util.c @@ -975,14 +975,14 @@ int cfg80211_change_iface(struct cfg80211_registered_device *rdev, !(rdev->wiphy.interface_modes & (1 << ntype))) return -EOPNOTSUPP; - /* if it's part of a bridge, reject changing type to station/ibss */ - if (netif_is_bridge_port(dev) && - (ntype == NL80211_IFTYPE_ADHOC || - ntype == NL80211_IFTYPE_STATION || - ntype == NL80211_IFTYPE_P2P_CLIENT)) - return -EBUSY; - if (ntype != otype) { + /* if it's part of a bridge, reject changing type to station/ibss */ + if (netif_is_bridge_port(dev) && + (ntype == NL80211_IFTYPE_ADHOC || + ntype == NL80211_IFTYPE_STATION || + ntype == NL80211_IFTYPE_P2P_CLIENT)) + return -EBUSY; + dev->ieee80211_ptr->use_4addr = false; dev->ieee80211_ptr->mesh_id_up_len = 0; wdev_lock(dev->ieee80211_ptr);