bonding: Fix multiple long standing offload races

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>

1 files changed, 5 insertions, 2 deletions

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;