diff options
| author | Michal Kazior <michal.kazior@tieto.com> | 2014-04-09 15:29:32 +0200 |
|---|---|---|
| committer | Johannes Berg <johannes.berg@intel.com> | 2014-04-25 17:08:30 +0200 |
| commit | 2b32713d72c093889fe20642f6a8bc42083267d2 (patch) | |
| tree | d5773d77a88b306fe4d8c48cc2173c1a49483dcb | |
| parent | 1f0d54cdcf822894cebebaa6cdc4e838c32bfb08 (diff) | |
mac80211: fix racy usage of chanctx->refcount
Channel context refcount is protected by
chanctx_mtx. Accessing the value without holding
the mutex is racy. RCU section didn't guarantee
anything here.
Theoretically ieee80211_channel_switch() could
fail to see refcount change and read "1" instead
of, e.g. "2". This means mac80211 could accept CSA
even though it shouldn't have.
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
| -rw-r--r-- | net/mac80211/cfg.c | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c index aa39381ca46d..9620d4fba0d1 100644 --- a/net/mac80211/cfg.c +++ b/net/mac80211/cfg.c @@ -3225,7 +3225,7 @@ int ieee80211_channel_switch(struct wiphy *wiphy, struct net_device *dev, { struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev); struct ieee80211_local *local = sdata->local; - struct ieee80211_chanctx_conf *chanctx_conf; + struct ieee80211_chanctx_conf *conf; struct ieee80211_chanctx *chanctx; int err, num_chanctx, changed = 0; @@ -3241,23 +3241,24 @@ int ieee80211_channel_switch(struct wiphy *wiphy, struct net_device *dev, &sdata->vif.bss_conf.chandef)) return -EINVAL; - rcu_read_lock(); - chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf); - if (!chanctx_conf) { - rcu_read_unlock(); + mutex_lock(&local->chanctx_mtx); + conf = rcu_dereference_protected(sdata->vif.chanctx_conf, + lockdep_is_held(&local->chanctx_mtx)); + if (!conf) { + mutex_unlock(&local->chanctx_mtx); return -EBUSY; } /* don't handle for multi-VIF cases */ - chanctx = container_of(chanctx_conf, struct ieee80211_chanctx, conf); + chanctx = container_of(conf, struct ieee80211_chanctx, conf); if (chanctx->refcount > 1) { - rcu_read_unlock(); + mutex_unlock(&local->chanctx_mtx); return -EBUSY; } num_chanctx = 0; list_for_each_entry_rcu(chanctx, &local->chanctx_list, list) num_chanctx++; - rcu_read_unlock(); + mutex_unlock(&local->chanctx_mtx); if (num_chanctx > 1) return -EBUSY; |