[PATCH net-next] bonding: don't need RTNL for ipsec helpers

[Jarod Wilson]

The bond_ipsec_* helpers don't need RTNL, and can potentially get called
without it being held, so switch from rtnl_dereference() to
rcu_dereference() to access bond struct data.

Lightly tested with xfrm bonding, no problems found, should address the
syzkaller bug referenced below.

Reported-by: syzbot+582c98032903dcc04...@syzkaller.appspotmail.com
CC: Huy Nguyen <h...@mellanox.com>
CC: Saeed Mahameed <sae...@mellanox.com>
CC: Jay Vosburgh <j.vosbu...@gmail.com>
CC: Veaceslav Falico <vfal...@gmail.com>
CC: Andy Gospodarek <a...@greyhouse.net>
CC: "David S. Miller" <da...@davemloft.net>
CC: Jeff Kirsher <jeffrey.t.kirs...@intel.com>
CC: Jakub Kicinski <k...@kernel.org>
CC: Steffen Klassert <steffen.klass...@secunet.com>
CC: Herbert Xu <herb...@gondor.apana.org.au>
CC: netdev@vger.kernel.org
CC: intel-wired-...@lists.osuosl.org
Signed-off-by: Jarod Wilson <ja...@redhat.com>
---
 drivers/net/bonding/bond_main.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index f886d97c4359..e2d491c4378c 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -390,7 +390,7 @@ static int bond_ipsec_add_sa(struct xfrm_state *xs)
                return -EINVAL;
 
        bond = netdev_priv(bond_dev);
-       slave = rtnl_dereference(bond->curr_active_slave);
+       slave = rcu_dereference(bond->curr_active_slave);
        xs->xso.real_dev = slave->dev;
        bond->xs = xs;
 
@@ -417,7 +417,7 @@ static void bond_ipsec_del_sa(struct xfrm_state *xs)
                return;
 
        bond = netdev_priv(bond_dev);
-       slave = rtnl_dereference(bond->curr_active_slave);
+       slave = rcu_dereference(bond->curr_active_slave);
 
        if (!slave)
                return;
@@ -442,7 +442,7 @@ static bool bond_ipsec_offload_ok(struct sk_buff *skb, 
struct xfrm_state *xs)
 {
        struct net_device *bond_dev = xs->xso.dev;
        struct bonding *bond = netdev_priv(bond_dev);
-       struct slave *curr_active = rtnl_dereference(bond->curr_active_slave);
+       struct slave *curr_active = rcu_dereference(bond->curr_active_slave);
        struct net_device *slave_dev = curr_active->dev;
 
        if (BOND_MODE(bond) != BOND_MODE_ACTIVEBACKUP)
-- 
2.20.1