mac80211: fix a crash in ieee80211_beacon_get_tim on change_interface

commit eb3e554b4b3a56386ef5214dbe0e3935a350178b upstream.

Some drivers (e.g. ath9k) do not always disable beacons when they're
supposed to. When an interface is changed using the change_interface op,
the mode specific sdata part is in an undefined state and trying to
get a beacon at this point can produce weird crashes.

To fix this, add a check for ieee80211_sdata_running before using
anything from the sdata.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index ab6355dd4ac0f7752edc3a9f85b5604f3b1fc4f5..fad02ea11520b23f6fe27db0029ca7a7f430803d 100644 (file)
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2175,6 +2175,9 @@ struct sk_buff *ieee80211_beacon_get_tim(struct ieee80211_hw *hw,
 
        sdata = vif_to_sdata(vif);
 
+       if (!ieee80211_sdata_running(sdata))
+               goto out;
+
        if (tim_offset)
                *tim_offset = 0;
        if (tim_length)