mac80211: fix scan vs. interface removal race
When we remove an interface, we can currently end up having
a pointer to it left in local->scan_sdata after it has been
set down, and then with a hardware scan the scan completion
can try to access it which is a bug. Alternatively, a scan
that started as a hardware scan may terminate as though it
was a software scan, if the timing is just right.
On SMP systems, software scan also has a similar problem,
just canceling the delayed work and setting a flag isn't
enough since it may be running concurrently; in this case
we would also never restore state of other interfaces.
This patch hopefully fixes the problems by always invoking
ieee80211_scan_completed or requiring it to be invoked by
the driver, I suspect the drivers that have ->hw_scan() are
buggy. The bug will not manifest itself unless you remove
the interface while hw-scanning which will also turn off
the hw, and then add a new interface which will be unusable
until you scan once.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index f4399e9..2772702 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -430,9 +430,20 @@
struct ieee80211_sub_if_data *sdata;
union iwreq_data wrqu;
+ if (WARN_ON(!local->sta_hw_scanning && !local->sta_sw_scanning))
+ return;
+
local->last_scan_completed = jiffies;
memset(&wrqu, 0, sizeof(wrqu));
- wireless_send_event(local->scan_sdata->dev, SIOCGIWSCAN, &wrqu, NULL);
+
+ /*
+ * local->scan_sdata could have been NULLed by the interface
+ * down code in case we were scanning on an interface that is
+ * being taken down.
+ */
+ sdata = local->scan_sdata;
+ if (sdata)
+ wireless_send_event(sdata->dev, SIOCGIWSCAN, &wrqu, NULL);
if (local->sta_hw_scanning) {
local->sta_hw_scanning = 0;
@@ -491,7 +502,10 @@
int skip;
unsigned long next_delay = 0;
- if (!local->sta_sw_scanning)
+ /*
+ * Avoid re-scheduling when the sdata is going away.
+ */
+ if (!netif_running(sdata->dev))
return;
switch (local->scan_state) {
@@ -570,9 +584,8 @@
break;
}
- if (local->sta_sw_scanning)
- queue_delayed_work(local->hw.workqueue, &local->scan_work,
- next_delay);
+ queue_delayed_work(local->hw.workqueue, &local->scan_work,
+ next_delay);
}
@@ -609,13 +622,16 @@
}
if (local->ops->hw_scan) {
- int rc = local->ops->hw_scan(local_to_hw(local),
- ssid, ssid_len);
- if (!rc) {
- local->sta_hw_scanning = 1;
- local->scan_sdata = scan_sdata;
+ int rc;
+
+ local->sta_hw_scanning = 1;
+ rc = local->ops->hw_scan(local_to_hw(local), ssid, ssid_len);
+ if (rc) {
+ local->sta_hw_scanning = 0;
+ return rc;
}
- return rc;
+ local->scan_sdata = scan_sdata;
+ return 0;
}
local->sta_sw_scanning = 1;