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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>
This commit is contained in:
Johannes Berg 2017-06-10 13:52:43 +03:00
parent 44f6d42cbd
commit c87905bec5
1 changed files with 28 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
net/mac80211/mlme.c
View File

@ -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);