mac80211: fix conn_mon_timer running after disassociate

Low level driver could pass rx frames to us after disassociate, what
can lead to run conn_mon_timer by ieee80211_sta_rx_notify(). That
is obviously wrong, but nothing happens until we unload modules and
resources are used after free. If kernel debugging is enabled following
warning could be observed:

WARNING: at lib/debugobjects.c:259 debug_print_object+0x65/0x70()
Hardware name: HP xw8600 Workstation
ODEBUG: free active (active state 0) object type: timer_list
Modules linked in: iwlagn(-) iwlcore mac80211 cfg80211 aes_x86_64 aes_generic fuse cpufreq_ondemand acpi_cpufreq freq_table mperf xt_physdev ipt_REJECT nf_conntrack_ipv4 nf_defrag_ipv4 iptable_filter ip_tables ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables ipv6 ext3 jbd dm_mirror dm_region_hash dm_log dm_mod uinput hp_wmi sparse_keymap sg wmi arc4 microcode serio_raw ecb tg3 shpchp rfkill ext4 mbcache jbd2 sr_mod cdrom sd_mod crc_t10dif firewire_ohci firewire_core crc_itu_t mptsas mptscsih mptbase scsi_transport_sas ahci libahci pata_acpi ata_generic ata_piix floppy nouveau ttm drm_kms_helper drm i2c_algo_bit i2c_core video [last unloaded: cfg80211]
Pid: 13827, comm: rmmod Tainted: G        W   2.6.38-rc4-wl+ #22
Call Trace:
 [<ffffffff810649cf>] ? warn_slowpath_common+0x7f/0xc0
 [<ffffffff81064ac6>] ? warn_slowpath_fmt+0x46/0x50
 [<ffffffff81226fc5>] ? debug_print_object+0x65/0x70
 [<ffffffff81227625>] ? debug_check_no_obj_freed+0x125/0x210
 [<ffffffff8109ebd7>] ? debug_check_no_locks_freed+0xf7/0x170
 [<ffffffff81156092>] ? kfree+0xc2/0x2f0
 [<ffffffff813ec5c5>] ? netdev_release+0x45/0x60
 [<ffffffff812f1067>] ? device_release+0x27/0xa0
 [<ffffffff81216ddd>] ? kobject_release+0x8d/0x1a0
 [<ffffffff81216d50>] ? kobject_release+0x0/0x1a0
 [<ffffffff812183b7>] ? kref_put+0x37/0x70
 [<ffffffff81216c57>] ? kobject_put+0x27/0x60
 [<ffffffff813d5d1b>] ? netdev_run_todo+0x1ab/0x270
 [<ffffffff813e771e>] ? rtnl_unlock+0xe/0x10
 [<ffffffffa0581188>] ? ieee80211_unregister_hw+0x58/0x120 [mac80211]
 [<ffffffffa0377ed7>] ? iwl_pci_remove+0xdb/0x22a [iwlagn]
 [<ffffffff8123cde2>] ? pci_device_remove+0x52/0x120
 [<ffffffff812f5205>] ? __device_release_driver+0x75/0xe0
 [<ffffffff812f5348>] ? driver_detach+0xd8/0xe0
 [<ffffffff812f4111>] ? bus_remove_driver+0x91/0x100
 [<ffffffff812f5b62>] ? driver_unregister+0x62/0xa0
 [<ffffffff8123d194>] ? pci_unregister_driver+0x44/0xa0
 [<ffffffffa0377df5>] ? iwl_exit+0x15/0x1c [iwlagn]
 [<ffffffff810ab492>] ? sys_delete_module+0x1a2/0x270
 [<ffffffff81498889>] ? trace_hardirqs_on_thunk+0x3a/0x3f
 [<ffffffff8100bf42>] ? system_call_fastpath+0x16/0x1b
Acked-by: NJohannes Berg <johannes@sipsolutions.net>
Signed-off-by: NStanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

net/mac80211/mlme.c

@@ -1033,6 +1033,12 @@ void ieee80211_sta_rx_notify(struct ieee80211_sub_if_data *sdata,
 	if (is_multicast_ether_addr(hdr->addr1))
 		return;
 
+	/*
+	 * In case we receive frames after disassociation.
+	 */
+	if (!sdata->u.mgd.associated)
+		return;
+
 	ieee80211_sta_reset_conn_monitor(sdata);
 }