[PATCH 07/12] bonding: Fix multiple long standing offload races

[Steffen Klassert <steffen.klassert@secunet.com>]

From: Cosmin Ratiu <cratiu@nvidia.com>

Refactor the bonding ipsec offload operations to fix a number of
long-standing control plane races between state migration and user
deletion and a few other issues.

xfrm state deletion can happen concurrently with
bond_change_active_slave() operation. This manifests itself as a
bond_ipsec_del_sa() call with x->lock held, followed by a
bond_ipsec_free_sa() a bit later from a wq. The alternate path of
these calls coming from xfrm_dev_state_flush() can't happen, as that
needs the RTNL lock and bond_change_active_slave() already holds it.

1. bond_ipsec_del_sa_all() might call xdo_dev_state_delete() a second
   time on an xfrm state that was concurrently killed. This is bad.
2. bond_ipsec_add_sa_all() can add a state on the new device, but
   pending bond_ipsec_free_sa() calls from the old device will then hit
   the WARN_ON() and then, worse, call xdo_dev_state_free() on the new
   device without a corresponding xdo_dev_state_delete().
3. Resolve a sleeping in atomic context introduced by the mentioned
   "Fixes" commit.

bond_ipsec_del_sa_all() and bond_ipsec_add_sa_all() now acquire x->lock
and check for x->km.state to help with problems 1 and 2. And since
xso.real_dev is now a private pointer managed by the bonding driver in
xfrm state, make better use of it to fully fix problems 1 and 2. In
bond_ipsec_del_sa_all(), set xso.real_dev to NULL while holding both the
mutex and x->lock, which makes sure that neither bond_ipsec_del_sa() nor
bond_ipsec_free_sa() could run concurrently.

Fix problem 3 by moving the list cleanup (which requires the mutex) from
bond_ipsec_del_sa() (called from atomic context) to bond_ipsec_free_sa()

Finally, simplify bond_ipsec_del_sa() and bond_ipsec_free_sa() by using
xso->real_dev directly, since it's now protected by locks and can be
trusted to always reflect the offload device.

Fixes: 2aeeef906d5a ("bonding: change ipsec_lock from spin lock to mutex")
Signed-off-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Reviewed-by: Hangbin Liu <liuhangbin@gmail.com>
Tested-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
---
 drivers/net/bonding/bond_main.c | 82 +++++++++++++++------------------
 include/net/xfrm.h              |  7 ++-
 2 files changed, 41 insertions(+), 48 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 14f7c9712ad4..8ed8c29659a0 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -545,7 +545,20 @@ static void bond_ipsec_add_sa_all(struct bonding *bond)
 			slave_warn(bond_dev, real_dev, "%s: failed to add SA\n", __func__);
 			continue;
 		}
+
+		spin_lock_bh(&ipsec->xs->lock);
+		/* xs might have been killed by the user during the migration
+		 * to the new dev, but bond_ipsec_del_sa() should have done
+		 * nothing, as xso.real_dev is NULL.
+		 * Delete it from the device we just added it to. The pending
+		 * bond_ipsec_free_sa() call will do the rest of the cleanup.
+		 */
+		if (ipsec->xs->km.state == XFRM_STATE_DEAD &&
+		    real_dev->xfrmdev_ops->xdo_dev_state_delete)
+			real_dev->xfrmdev_ops->xdo_dev_state_delete(real_dev,
+								    ipsec->xs);
 		ipsec->xs->xso.real_dev = real_dev;
+		spin_unlock_bh(&ipsec->xs->lock);
 	}
 out:
 	mutex_unlock(&bond->ipsec_lock);
@@ -560,48 +573,20 @@ static void bond_ipsec_del_sa(struct net_device *bond_dev,
 			      struct xfrm_state *xs)
 {
 	struct net_device *real_dev;
-	netdevice_tracker tracker;
-	struct bond_ipsec *ipsec;
-	struct bonding *bond;
-	struct slave *slave;
 
-	if (!bond_dev)
+	if (!bond_dev || !xs->xso.real_dev)
 		return;
 
-	rcu_read_lock();
-	bond = netdev_priv(bond_dev);
-	slave = rcu_dereference(bond->curr_active_slave);
-	real_dev = slave ? slave->dev : NULL;
-	netdev_hold(real_dev, &tracker, GFP_ATOMIC);
-	rcu_read_unlock();
-
-	if (!slave)
-		goto out;
-
-	if (!xs->xso.real_dev)
-		goto out;
-
-	WARN_ON(xs->xso.real_dev != real_dev);
+	real_dev = xs->xso.real_dev;
 
 	if (!real_dev->xfrmdev_ops ||
 	    !real_dev->xfrmdev_ops->xdo_dev_state_delete ||
 	    netif_is_bond_master(real_dev)) {
 		slave_warn(bond_dev, real_dev, "%s: no slave xdo_dev_state_delete\n", __func__);
-		goto out;
+		return;
 	}
 
 	real_dev->xfrmdev_ops->xdo_dev_state_delete(real_dev, xs);
-out:
-	netdev_put(real_dev, &tracker);
-	mutex_lock(&bond->ipsec_lock);
-	list_for_each_entry(ipsec, &bond->ipsec_list, list) {
-		if (ipsec->xs == xs) {
-			list_del(&ipsec->list);
-			kfree(ipsec);
-			break;
-		}
-	}
-	mutex_unlock(&bond->ipsec_lock);
 }
 
 static void bond_ipsec_del_sa_all(struct bonding *bond)
@@ -629,9 +614,15 @@ static void bond_ipsec_del_sa_all(struct bonding *bond)
 				   __func__);
 			continue;
 		}
+
+		spin_lock_bh(&ipsec->xs->lock);
 		ipsec->xs->xso.real_dev = NULL;
-		real_dev->xfrmdev_ops->xdo_dev_state_delete(real_dev,
-							    ipsec->xs);
+		/* Don't double delete states killed by the user. */
+		if (ipsec->xs->km.state != XFRM_STATE_DEAD)
+			real_dev->xfrmdev_ops->xdo_dev_state_delete(real_dev,
+								    ipsec->xs);
+		spin_unlock_bh(&ipsec->xs->lock);
+
 		if (real_dev->xfrmdev_ops->xdo_dev_state_free)
 			real_dev->xfrmdev_ops->xdo_dev_state_free(real_dev,
 								  ipsec->xs);
@@ -643,34 +634,33 @@ static void bond_ipsec_free_sa(struct net_device *bond_dev,
 			       struct xfrm_state *xs)
 {
 	struct net_device *real_dev;
-	netdevice_tracker tracker;
+	struct bond_ipsec *ipsec;
 	struct bonding *bond;
-	struct slave *slave;
 
 	if (!bond_dev)
 		return;
 
-	rcu_read_lock();
 	bond = netdev_priv(bond_dev);
-	slave = rcu_dereference(bond->curr_active_slave);
-	real_dev = slave ? slave->dev : NULL;
-	netdev_hold(real_dev, &tracker, GFP_ATOMIC);
-	rcu_read_unlock();
-
-	if (!slave)
-		goto out;
 
+	mutex_lock(&bond->ipsec_lock);
 	if (!xs->xso.real_dev)
 		goto out;
 
-	WARN_ON(xs->xso.real_dev != real_dev);
+	real_dev = xs->xso.real_dev;
 
 	xs->xso.real_dev = NULL;
-	if (real_dev && real_dev->xfrmdev_ops &&
+	if (real_dev->xfrmdev_ops &&
 	    real_dev->xfrmdev_ops->xdo_dev_state_free)
 		real_dev->xfrmdev_ops->xdo_dev_state_free(real_dev, xs);
 out:
-	netdev_put(real_dev, &tracker);
+	list_for_each_entry(ipsec, &bond->ipsec_list, list) {
+		if (ipsec->xs == xs) {
+			list_del(&ipsec->list);
+			kfree(ipsec);
+			break;
+		}
+	}
+	mutex_unlock(&bond->ipsec_lock);
 }
 
 /**
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 3d2f6c879311..b7e8f3f49627 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -154,8 +154,11 @@ struct xfrm_dev_offload {
 	 */
 	struct net_device	*dev;
 	netdevice_tracker	dev_tracker;
-	/* This is a private pointer used by the bonding driver.
-	 * Device drivers should not use it.
+	/* This is a private pointer used by the bonding driver (and eventually
+	 * should be moved there). Device drivers should not use it.
+	 * Protected by xfrm_state.lock AND bond.ipsec_lock in most cases,
+	 * except in the .xdo_dev_state_del() flow, where only xfrm_state.lock
+	 * is held.
 	 */
 	struct net_device	*real_dev;
 	unsigned long		offload_handle;
-- 
2.34.1