[patch 047/176] mac80211: fix a crash in ieee80211_beacon_get_tim on change_interface

[Greg KH]

2.6.36-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Felix Fietkau <nbd@xxxxxxxxxxx>

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@xxxxxxxxxxx>
Signed-off-by: John W. Linville <linville@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 net/mac80211/tx.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2175,6 +2175,9 @@ struct sk_buff *ieee80211_beacon_get_tim
 
 	sdata = vif_to_sdata(vif);
 
+	if (!ieee80211_sdata_running(sdata))
+		goto out;
+
 	if (tim_offset)
 		*tim_offset = 0;
 	if (tim_length)


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