[PATCH net-2.6] pkt_sched: gen_estimator: add a new lock

[Eric Dumazet <eric.dumazet@gmail.com>]

Le lundi 07 juin 2010 à 18:56 +0200, Eric Dumazet a écrit :
> > 
> > For your information, bug is already there before my patch.
> > 
> > So this est_lock is a wrong protection, in the sense its so convoluted
> > that nobody but you and me even noticed it was buggy in the first place.
> > 
> > (see commit 5d944c640b4 for a first patch)
> > 
> > 
> 
> Here is v2 of the patch.
> 
> Even if its a bug correction, I cooked it for net-next-2.6 since bug
> probably never occured, and patch is too large to be sent to
> net-2.6/linux-2.6 before testing.
> 
> Another bug comes from net/netfilter/xt_RATEEST.c : It apparently
> calls gen_kill_estimator() / gen_new_estimator() without holding RTNL ?
> 
> So we should add another lock to protect things (est_root, elist[], ...)
> 
> David, I can send a net-2.6 patch for this one, since it should be small
> enough. If yes, I'll respin this patch of course ;)

[PATCH net-2.6] pkt_sched: gen_estimator: add a new lock

gen_kill_estimator() / gen_new_estimator() is not always called with
RTNL held.

net/netfilter/xt_RATEEST.c is one user of these API that do not hold
RTNL, so random corruptions can occur between "tc" and "iptables"

Add a new fine grained lock instead of trying to use RTNL in xt_RATEEST

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
 net/core/gen_estimator.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/core/gen_estimator.c b/net/core/gen_estimator.c
index cf8e703..3d11203 100644
--- a/net/core/gen_estimator.c
+++ b/net/core/gen_estimator.c
@@ -107,6 +107,7 @@ static DEFINE_RWLOCK(est_lock);
 
 /* Protects against soft lockup during large deletion */
 static struct rb_root est_root = RB_ROOT;
+static DEFINE_SPINLOCK(est_tree_lock);
 
 static void est_timer(unsigned long arg)
 {
@@ -201,7 +202,6 @@ struct gen_estimator *gen_find_node(const struct gnet_stats_basic_packed *bstats
  *
  * Returns 0 on success or a negative error code.
  *
- * NOTE: Called under rtnl_mutex
  */
 int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
 		      struct gnet_stats_rate_est *rate_est,
@@ -222,6 +222,7 @@ int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
 	if (est == NULL)
 		return -ENOBUFS;
 
+	spin_lock(&est_tree_lock);
 	idx = parm->interval + 2;
 	est->bstats = bstats;
 	est->rate_est = rate_est;
@@ -242,6 +243,7 @@ int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
 
 	list_add_rcu(&est->list, &elist[idx].list);
 	gen_add_node(est);
+	spin_unlock(&est_tree_lock);
 
 	return 0;
 }
@@ -261,13 +263,13 @@ static void __gen_kill_estimator(struct rcu_head *head)
  *
  * Removes the rate estimator specified by &bstats and &rate_est.
  *
- * NOTE: Called under rtnl_mutex
  */
 void gen_kill_estimator(struct gnet_stats_basic_packed *bstats,
 			struct gnet_stats_rate_est *rate_est)
 {
 	struct gen_estimator *e;
 
+	spin_lock(&est_tree_lock);
 	while ((e = gen_find_node(bstats, rate_est))) {
 		rb_erase(&e->node, &est_root);
 
@@ -278,6 +280,7 @@ void gen_kill_estimator(struct gnet_stats_basic_packed *bstats,
 		list_del_rcu(&e->list);
 		call_rcu(&e->e_rcu, __gen_kill_estimator);
 	}
+	spin_unlock(&est_tree_lock);
 }
 EXPORT_SYMBOL(gen_kill_estimator);