regulatory: use RCU to protect global and wiphy regdomains

To simplify the locking and not require cfg80211_mutex
(which nl80211 uses to access the global regdomain) and
also to make it possible for drivers to access their
wiphy->regd safely, use RCU to protect these pointers.

Acked-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 18 insertions, 17 deletions

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index b387deaf1132..b3cf7cc0d4a1 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -3787,12 +3787,8 @@ static int nl80211_req_set_reg(struct sk_buff *skb, struct genl_info *info)
          * window between nl80211_init() and regulatory_init(), if that is
          * even possible.
          */
-        mutex_lock(&cfg80211_mutex);
-        if (unlikely(!cfg80211_regdomain)) {
-                mutex_unlock(&cfg80211_mutex);
+        if (unlikely(!rcu_access_pointer(cfg80211_regdomain)))
                 return -EINPROGRESS;
-        }
-        mutex_unlock(&cfg80211_mutex);
 
         if (!info->attrs[NL80211_ATTR_REG_ALPHA2])
                 return -EINVAL;
@@ -4152,6 +4148,7 @@ static int nl80211_update_mesh_config(struct sk_buff *skb,
 
 static int nl80211_get_reg(struct sk_buff *skb, struct genl_info *info)
 {
+        const struct ieee80211_regdomain *regdom;
         struct sk_buff *msg;
         void *hdr = NULL;
         struct nlattr *nl_reg_rules;
@@ -4174,35 +4171,36 @@ static int nl80211_get_reg(struct sk_buff *skb, struct genl_info *info)
         if (!hdr)
                 goto put_failure;
 
-        if (nla_put_string(msg, NL80211_ATTR_REG_ALPHA2,
-                           cfg80211_regdomain->alpha2) ||
-            (cfg80211_regdomain->dfs_region &&
-             nla_put_u8(msg, NL80211_ATTR_DFS_REGION,
-                        cfg80211_regdomain->dfs_region)))
-                goto nla_put_failure;
-
         if (reg_last_request_cell_base() &&
             nla_put_u32(msg, NL80211_ATTR_USER_REG_HINT_TYPE,
                         NL80211_USER_REG_HINT_CELL_BASE))
                 goto nla_put_failure;
 
+        rcu_read_lock();
+        regdom = rcu_dereference(cfg80211_regdomain);
+
+        if (nla_put_string(msg, NL80211_ATTR_REG_ALPHA2, regdom->alpha2) ||
+            (regdom->dfs_region &&
+             nla_put_u8(msg, NL80211_ATTR_DFS_REGION, regdom->dfs_region)))
+                goto nla_put_failure_rcu;
+
         nl_reg_rules = nla_nest_start(msg, NL80211_ATTR_REG_RULES);
         if (!nl_reg_rules)
-                goto nla_put_failure;
+                goto nla_put_failure_rcu;
 
-        for (i = 0; i < cfg80211_regdomain->n_reg_rules; i++) {
+        for (i = 0; i < regdom->n_reg_rules; i++) {
                 struct nlattr *nl_reg_rule;
                 const struct ieee80211_reg_rule *reg_rule;
                 const struct ieee80211_freq_range *freq_range;
                 const struct ieee80211_power_rule *power_rule;
 
-                reg_rule = &cfg80211_regdomain->reg_rules[i];
+                reg_rule = &regdom->reg_rules[i];
                 freq_range = &reg_rule->freq_range;
                 power_rule = &reg_rule->power_rule;
 
                 nl_reg_rule = nla_nest_start(msg, i);
                 if (!nl_reg_rule)
-                        goto nla_put_failure;
+                        goto nla_put_failure_rcu;
 
                 if (nla_put_u32(msg, NL80211_ATTR_REG_RULE_FLAGS,
                                 reg_rule->flags) ||
@@ -4216,10 +4214,11 @@ static int nl80211_get_reg(struct sk_buff *skb, struct genl_info *info)
                                 power_rule->max_antenna_gain) ||
                     nla_put_u32(msg, NL80211_ATTR_POWER_RULE_MAX_EIRP,
                                 power_rule->max_eirp))
-                        goto nla_put_failure;
+                        goto nla_put_failure_rcu;
 
                 nla_nest_end(msg, nl_reg_rule);
         }
+        rcu_read_unlock();
 
         nla_nest_end(msg, nl_reg_rules);
 
@@ -4227,6 +4226,8 @@ static int nl80211_get_reg(struct sk_buff *skb, struct genl_info *info)
         err = genlmsg_reply(msg, info);
         goto out;
 
+nla_put_failure_rcu:
+        rcu_read_unlock();
 nla_put_failure:
         genlmsg_cancel(msg, hdr);
 put_failure: