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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Janusz Dziedzic <janusz.dziedzic@gmail.com>,
        Johannes Berg <johannes.berg@intel.com>
Subject: [PATCH 5.10 51/77] cfg80211: correct bridge/4addr mode check
Date:   Mon,  1 Nov 2021 10:17:39 +0100
Message-Id: <20211101082522.465847188@linuxfoundation.org>
In-Reply-To: <20211101082511.254155853@linuxfoundation.org>
References: <20211101082511.254155853@linuxfoundation.org>
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From: Janusz Dziedzic <janusz.dziedzic@gmail.com>

commit 689a0a9f505f7bffdefe6f17fddb41c8ab6344f6 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/wireless/util.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -1028,14 +1028,14 @@ int cfg80211_change_iface(struct cfg8021
 	    !(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);