mac80211: fix memory leak

commit ea32f065 upstream.

On error we jumped to the error label and returned the error code but we
missed releasing sinfo.

Fixes: 5fe74014172d ("mac80211: avoid excessive stack usage in sta_info")
Reviewed-by: Julian Calaby <julian.calaby@gmail.com>
Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
[bwh: Backported to 3.2: there's no out_err label but there is another
 error case that would leak sinfo]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

net/mac80211/sta_info.c

@@ -362,8 +362,10 @@ static int sta_info_finish_insert(struct sta_info *sta,
 					     u.ap);
 		err = drv_sta_add(local, sdata, &sta->sta);
 		if (err) {
-			if (!async)
+			if (!async) {
+				kfree(sinfo);
 				return err;
+			}
 			printk(KERN_DEBUG "%s: failed to add IBSS STA %pM to "
 					  "driver (%d) - keeping it anyway.\n",
 			       sdata->name, sta->sta.addr, err);