mac80211: check interface is down before type change

For some strange reason the netif_running() check
ended up after the actual type change instead of
before, potentially causing all kinds of problems
if the interface is up while changing the type;
one of the problems manifests itself as a warning:

WARNING: at net/mac80211/iface.c:651 ieee80211_teardown_sdata+0xda/0x1a0 [mac80211]()
Hardware name: Aspire one
Pid: 2596, comm: wpa_supplicant Tainted: G        W  2.6.31-10-generic #32-Ubuntu
Call Trace:
 [] warn_slowpath_common+0x6d/0xa0
 [] warn_slowpath_null+0x15/0x20
 [] ieee80211_teardown_sdata+0xda/0x1a0 [mac80211]
 [] ieee80211_if_change_type+0x4a/0xc0 [mac80211]
 [] ieee80211_change_iface+0x61/0xa0 [mac80211]
 [] cfg80211_wext_siwmode+0xc7/0x120 [cfg80211]
 [] ioctl_standard_call+0x58/0xf0

(http://www.kerneloops.org/searchweek.php?search=ieee80211_teardown_sdata)

Cc: Arjan van de Ven <arjan@infradead.org>
Cc: stable@kernel.org
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 5608f6c68413..7b5131bd6fa1 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -72,6 +72,9 @@ static int ieee80211_change_iface(struct wiphy *wiphy,
         struct ieee80211_sub_if_data *sdata;
         int ret;
 
+        if (netif_running(dev))
+                return -EBUSY;
+
         if (!nl80211_type_check(type))
                 return -EINVAL;
 
@@ -81,9 +84,6 @@ static int ieee80211_change_iface(struct wiphy *wiphy,
         if (ret)
                 return ret;
 
-        if (netif_running(sdata->dev))
-                return -EBUSY;
-
         if (ieee80211_vif_is_mesh(&sdata->vif) && params->mesh_id_len)
                 ieee80211_sdata_set_mesh_id(sdata,
                                             params->mesh_id_len,