The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 689a0a9f505f7bffdefe6f17fddb41c8ab6344f6 Mon Sep 17 00:00:00 2001

From: Janusz Dziedzic janusz.dziedzic@gmail.com Date: Sun, 24 Oct 2021 22:15:46 +0200 Subject: [PATCH] cfg80211: correct bridge/4addr mode check

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@gmail.com Link: https://lore.kernel.org/r/20211024201546.614379-1-janusz.dziedzic@gmail.com [add fixes tag, fix indentation, edit commit log] Signed-off-by: Johannes Berg johannes.berg@intel.com

diff --git a/net/wireless/util.c b/net/wireless/util.c index 18dba3d7c638..a1a99a574984 100644 --- a/net/wireless/util.c +++ b/net/wireless/util.c @@ -1028,14 +1028,14 @@ 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);