mac80211: fix key vs. sta locking problems

Up to now, key manipulation is supposed to run under RTNL to
avoid concurrent manipulations and also allow the set_key()
hardware callback to sleep. This is not feasible because STA
structs are rcu-protected and thus a lot of operations there
cannot take the RTNL. Also, key references are rcu-protected
so we cannot do things atomically.

This patch changes key locking completely:
 * key operations are now atomic
 * hardware crypto offload is enabled and disabled from
   a workqueue, due to that key freeing is also delayed
 * debugfs code is also run from a workqueue
 * keys reference STAs (and vice versa!) so during STA
   unlink the STAs key reference is removed but not the
   keys STA reference, to avoid races key todo work is
   run before STA destruction.
 * fewer STA operations now need the RTNL which was
   required due to key operations

This fixes the locking problems lockdep pointed out and also
makes things more light-weight because the rtnl isn't required
as much.

Note that the key todo lock/key mutex are global locks, this
is not required, of course, they could be per-hardware instead.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 16 insertions, 4 deletions

diff --git a/net/mac80211/ieee80211_key.h b/net/mac80211/ieee80211_key.h
index d670e6dbfa3..467890c6fe8 100644
--- a/net/mac80211/ieee80211_key.h
+++ b/net/mac80211/ieee80211_key.h
@@ -51,13 +51,19 @@ struct sta_info;
  *
  * @KEY_FLAG_UPLOADED_TO_HARDWARE: Indicates that this key is present
  *	in the hardware for TX crypto hardware acceleration.
- * @KEY_FLAG_REMOVE_FROM_HARDWARE: Indicates to the key code that this
- *	key is present in the hardware (but it cannot be used for
- *	hardware acceleration any more!)
+ * @KEY_FLAG_TODO_DELETE: Key is marked for deletion and will, after an
+ *	RCU grace period, no longer be reachable other than from the
+ *	todo list.
+ * @KEY_FLAG_TODO_HWACCEL: Key needs to be added to hardware acceleration.
+ * @KEY_FLAG_TODO_DEFKEY: Key is default key and debugfs needs to be updated.
+ * @KEY_FLAG_TODO_ADD_DEBUGFS: Key needs to be added to debugfs.
  */
 enum ieee80211_internal_key_flags {
 	KEY_FLAG_UPLOADED_TO_HARDWARE	= BIT(0),
-	KEY_FLAG_REMOVE_FROM_HARDWARE	= BIT(1),
+	KEY_FLAG_TODO_DELETE		= BIT(1),
+	KEY_FLAG_TODO_HWACCEL		= BIT(2),
+	KEY_FLAG_TODO_DEFKEY		= BIT(3),
+	KEY_FLAG_TODO_ADD_DEBUGFS	= BIT(4),
 };
 
 struct ieee80211_key {
@@ -65,8 +71,12 @@ struct ieee80211_key {
 	struct ieee80211_sub_if_data *sdata;
 	struct sta_info *sta;
 
+	/* for sdata list */
 	struct list_head list;
+	/* for todo list */
+	struct list_head todo;
 
+	/* protected by todo lock! */
 	unsigned int flags;
 
 	union {
@@ -142,4 +152,6 @@ void ieee80211_free_keys(struct ieee80211_sub_if_data *sdata);
 void ieee80211_enable_keys(struct ieee80211_sub_if_data *sdata);
 void ieee80211_disable_keys(struct ieee80211_sub_if_data *sdata);
 
+void ieee80211_key_todo(void);
+
 #endif /* IEEE80211_KEY_H */