mac80211: make scan_sdata pointer usable with RCU

Making the scan_sdata pointer usable with RCU makes
it possible to dereference it in the RX path to see
if a received frame actually matches the interface
that is scanning. This is just preparations, making
the pointer __rcu.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

3 files changed, 30 insertions, 14 deletions

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index c3241c3ec6d1..9f2534a41243 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -972,7 +972,7 @@ struct ieee80211_local {
         unsigned long leave_oper_channel_time;
         enum mac80211_scan_state next_scan_state;
         struct delayed_work scan_work;
-        struct ieee80211_sub_if_data *scan_sdata;
+        struct ieee80211_sub_if_data __rcu *scan_sdata;
         enum nl80211_channel_type _oper_channel_type;
         struct ieee80211_channel *oper_channel, *csa_channel;
 
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index b1edf60fbba7..e3c49748ce8f 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -112,10 +112,11 @@ static u32 __ieee80211_recalc_idle(struct ieee80211_local *local)
                 }
         }
 
-        if (local->scan_sdata &&
-            !(local->hw.flags & IEEE80211_HW_SCAN_WHILE_IDLE)) {
+        sdata = rcu_dereference_protected(local->scan_sdata,
+                                          lockdep_is_held(&local->mtx));
+        if (sdata && !(local->hw.flags & IEEE80211_HW_SCAN_WHILE_IDLE)) {
                 scanning = true;
-                local->scan_sdata->vif.bss_conf.idle = false;
+                sdata->vif.bss_conf.idle = false;
         }
 
         list_for_each_entry(sdata, &local->interfaces, list) {
@@ -628,7 +629,7 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
 
         clear_bit(SDATA_STATE_RUNNING, &sdata->state);
 
-        if (local->scan_sdata == sdata)
+        if (rcu_access_pointer(local->scan_sdata) == sdata)
                 ieee80211_scan_cancel(local);
 
         /*
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 1ff04f689d1f..704dcf847761 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -293,7 +293,13 @@ static void __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted,
                 return;
 
         if (was_hw_scan && !aborted && ieee80211_prep_hw_scan(local)) {
-                int rc = drv_hw_scan(local, local->scan_sdata, local->hw_scan_req);
+                int rc;
+
+                rc = drv_hw_scan(local,
+                        rcu_dereference_protected(local->scan_sdata,
+                                                  lockdep_is_held(&local->mtx)),
+                        local->hw_scan_req);
+
                 if (rc == 0)
                         return;
         }
@@ -394,7 +400,10 @@ void ieee80211_run_deferred_scan(struct ieee80211_local *local)
         if (!local->scan_req || local->scanning)
                 return;
 
-        if (!ieee80211_can_scan(local, local->scan_sdata))
+        if (!ieee80211_can_scan(local,
+                                rcu_dereference_protected(
+                                        local->scan_sdata,
+                                        lockdep_is_held(&local->mtx))))
                 return;
 
         ieee80211_queue_delayed_work(&local->hw, &local->scan_work,
@@ -405,9 +414,12 @@ static void ieee80211_scan_state_send_probe(struct ieee80211_local *local,
                                             unsigned long *next_delay)
 {
         int i;
-        struct ieee80211_sub_if_data *sdata = local->scan_sdata;
+        struct ieee80211_sub_if_data *sdata;
         enum ieee80211_band band = local->hw.conf.channel->band;
 
+        sdata = rcu_dereference_protected(local->scan_sdata,
+                                          lockdep_is_held(&local->mtx));;
+
         for (i = 0; i < local->scan_req->n_ssids; i++)
                 ieee80211_send_probe_req(
                         sdata, NULL,
@@ -439,7 +451,7 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
         if (!ieee80211_can_scan(local, sdata)) {
                 /* wait for the work to finish/time out */
                 local->scan_req = req;
-                local->scan_sdata = sdata;
+                rcu_assign_pointer(local->scan_sdata, sdata);
                 return 0;
         }
 
@@ -473,7 +485,7 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
         }
 
         local->scan_req = req;
-        local->scan_sdata = sdata;
+        rcu_assign_pointer(local->scan_sdata, sdata);
 
         if (local->ops->hw_scan) {
                 __set_bit(SCAN_HW_SCANNING, &local->scanning);
@@ -533,7 +545,7 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
                 ieee80211_recalc_idle(local);
 
                 local->scan_req = NULL;
-                local->scan_sdata = NULL;
+                rcu_assign_pointer(local->scan_sdata, NULL);
         }
 
         return rc;
@@ -720,7 +732,8 @@ void ieee80211_scan_work(struct work_struct *work)
 
         mutex_lock(&local->mtx);
 
-        sdata = local->scan_sdata;
+        sdata = rcu_dereference_protected(local->scan_sdata,
+                                          lockdep_is_held(&local->mtx));
 
         /* When scanning on-channel, the first-callback means completed. */
         if (test_bit(SCAN_ONCHANNEL_SCANNING, &local->scanning)) {
@@ -741,7 +754,7 @@ void ieee80211_scan_work(struct work_struct *work)
                 int rc;
 
                 local->scan_req = NULL;
-                local->scan_sdata = NULL;
+                rcu_assign_pointer(local->scan_sdata, NULL);
 
                 rc = __ieee80211_start_scan(sdata, req);
                 if (rc) {
@@ -893,7 +906,9 @@ void ieee80211_scan_cancel(struct ieee80211_local *local)
 
         if (test_bit(SCAN_HW_SCANNING, &local->scanning)) {
                 if (local->ops->cancel_hw_scan)
-                        drv_cancel_hw_scan(local, local->scan_sdata);
+                        drv_cancel_hw_scan(local,
+                                rcu_dereference_protected(local->scan_sdata,
+                                                lockdep_is_held(&local->mtx)));
                 goto out;
         }