mac80211: set bss_info data before configuring the channel
When mac80211 changes the channel, it also calls into the driver's
bss_info_changed() callback, e.g. with BSS_CHANGED_IDLE. The driver
may, like iwlwifi does, access more data from bss_info in that case
and iwlwifi accesses the basic_rates bitmap, but if changing from a
band with more (basic) rates to one with fewer, an out-of-bounds
access of the rate array may result.
While we can't avoid having invalid data at some point in time, we
can avoid having it while we call the driver - so set up all the
data before configuring the channel, and then apply it afterwards.
This fixes https://bugzilla.kernel.org/show_bug.cgi?id=195677
Reported-by: Johannes Hirte <johannes.hirte@datenkhaos.de>
Tested-by: Johannes Hirte <johannes.hirte@datenkhaos.de>
Debugged-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 2f46db7..cc8e6ea 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -4392,15 +4392,19 @@ static int ieee80211_prep_connection(struct ieee80211_sub_if_data *sdata,
return -ENOMEM;
}
- if (new_sta || override) {
- err = ieee80211_prep_channel(sdata, cbss);
- if (err) {
- if (new_sta)
- sta_info_free(local, new_sta);
- return -EINVAL;
- }
- }
-
+ /*
+ * Set up the information for the new channel before setting the
+ * new channel. We can't - completely race-free - change the basic
+ * rates bitmap and the channel (sband) that it refers to, but if
+ * we set it up before we at least avoid calling into the driver's
+ * bss_info_changed() method with invalid information (since we do
+ * call that from changing the channel - only for IDLE and perhaps
+ * some others, but ...).
+ *
+ * So to avoid that, just set up all the new information before the
+ * channel, but tell the driver to apply it only afterwards, since
+ * it might need the new channel for that.
+ */
if (new_sta) {
u32 rates = 0, basic_rates = 0;
bool have_higher_than_11mbit;
@@ -4471,8 +4475,22 @@ static int ieee80211_prep_connection(struct ieee80211_sub_if_data *sdata,
sdata->vif.bss_conf.sync_dtim_count = 0;
}
rcu_read_unlock();
+ }
- /* tell driver about BSSID, basic rates and timing */
+ if (new_sta || override) {
+ err = ieee80211_prep_channel(sdata, cbss);
+ if (err) {
+ if (new_sta)
+ sta_info_free(local, new_sta);
+ return -EINVAL;
+ }
+ }
+
+ if (new_sta) {
+ /*
+ * tell driver about BSSID, basic rates and timing
+ * this was set up above, before setting the channel
+ */
ieee80211_bss_info_change_notify(sdata,
BSS_CHANGED_BSSID | BSS_CHANGED_BASIC_RATES |
BSS_CHANGED_BEACON_INT);