The ath_rate_sample function in the ath_rate/sample/sample.c sample code in MadWifi before 0.9.3 allows remote attackers to cause a denial of service (failed KASSERT and system crash) by moving a connected system to a location with low signal strength, and possibly other vectors related to a race condition between interface enabling and packet transmission.
http://www.novell.com/linux/security/advisories/2007_14_sr.html
http://www.mandriva.com/security/advisories?name=MDKSA-2007:082
http://secunia.com/advisories/26083
http://secunia.com/advisories/24841