There are a few problems in the IBSS code:
a) it tries to activate interfaces that are down after scanning
b) it crashes after scanning on an IBSS iface that isn't active
c) since the ssid_len is used as a flag, need to make it visible
only after all other settings are set, this helps protect
against b)
For b), we get a system crash:
wlan0: Creating new IBSS network, BSSID ce:f9:88:76:1e:4d
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<...>] ieee80211_sta_find_ibss+0x294/0x37d [mac80211]
Call Trace:
[<...>] ieee80211_ibss_notify_scan_completed+0x0/0x88 [mac80211]
Signed-off-by: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
---
net/mac80211/ibss.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
--- wireless-testing.orig/net/mac80211/ibss.c 2009-04-23 11:18:12.000000000 +0200
+++ wireless-testing/net/mac80211/ibss.c 2009-04-23 11:39:16.000000000 +0200
@@ -793,8 +793,12 @@ void ieee80211_ibss_notify_scan_complete
mutex_lock(&local->iflist_mtx);
list_for_each_entry(sdata, &local->interfaces, list) {
+ if (!netif_running(sdata->dev))
+ continue;
if (sdata->vif.type != NL80211_IFTYPE_ADHOC)
continue;
+ if (!sdata->u.ibss.ssid_len)
+ continue;
sdata->u.ibss.last_scan_completed = jiffies;
ieee80211_sta_find_ibss(sdata);
}
@@ -834,9 +838,6 @@ int ieee80211_ibss_join(struct ieee80211
{
struct sk_buff *skb;
- memcpy(sdata->u.ibss.ssid, params->ssid, IEEE80211_MAX_SSID_LEN);
- sdata->u.ibss.ssid_len = params->ssid_len;
-
if (params->bssid) {
memcpy(sdata->u.ibss.bssid, params->bssid, ETH_ALEN);
sdata->u.ibss.fixed_bssid = true;
@@ -868,6 +869,17 @@ int ieee80211_ibss_join(struct ieee80211
sdata->u.ibss.state = IEEE80211_IBSS_MLME_SEARCH;
sdata->u.ibss.ibss_join_req = jiffies;
+ memcpy(sdata->u.ibss.ssid, params->ssid, IEEE80211_MAX_SSID_LEN);
+
+ /*
+ * The ssid_len setting below is used to see whether
+ * we are active, and we need all other settings
+ * before that may get visible.
+ */
+ mb();
+
+ sdata->u.ibss.ssid_len = params->ssid_len;
+
ieee80211_recalc_radio_enable(sdata->local);
set_bit(IEEE80211_IBSS_REQ_RUN, &sdata->u.ibss.request);
--
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