From: Vladimir Oltean vladimir.oltean@nxp.com
[ Upstream commit 99f62a746066fa436aa15d4606a538569540db08 ]
When calling the RCU brother of br_vlan_get_pvid(), lockdep warns:
============================= WARNING: suspicious RCU usage 5.9.0-rc3-01631-g13c17acb8e38-dirty #814 Not tainted ----------------------------- net/bridge/br_private.h:1054 suspicious rcu_dereference_protected() usage!
Call trace: lockdep_rcu_suspicious+0xd4/0xf8 __br_vlan_get_pvid+0xc0/0x100 br_vlan_get_pvid_rcu+0x78/0x108
The warning is because br_vlan_get_pvid_rcu() calls nbp_vlan_group() which calls rtnl_dereference() instead of rcu_dereference(). In turn, rtnl_dereference() calls rcu_dereference_protected() which assumes operation under an RCU write-side critical section, which obviously is not the case here. So, when the incorrect primitive is used to access the RCU-protected VLAN group pointer, READ_ONCE() is not used, which may cause various unexpected problems.
I'm sad to say that br_vlan_get_pvid() and br_vlan_get_pvid_rcu() cannot share the same implementation. So fix the bug by splitting the 2 functions, and making br_vlan_get_pvid_rcu() retrieve the VLAN groups under proper locking annotations.
Fixes: 7582f5b70f9a ("bridge: add br_vlan_get_pvid_rcu()") Signed-off-by: Vladimir Oltean vladimir.oltean@nxp.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/bridge/br_vlan.c | 27 +++++++++++++++++---------- 1 file changed, 17 insertions(+), 10 deletions(-)
--- a/net/bridge/br_vlan.c +++ b/net/bridge/br_vlan.c @@ -1288,11 +1288,13 @@ void br_vlan_get_stats(const struct net_ } }
-static int __br_vlan_get_pvid(const struct net_device *dev, - struct net_bridge_port *p, u16 *p_pvid) +int br_vlan_get_pvid(const struct net_device *dev, u16 *p_pvid) { struct net_bridge_vlan_group *vg; + struct net_bridge_port *p;
+ ASSERT_RTNL(); + p = br_port_get_check_rtnl(dev); if (p) vg = nbp_vlan_group(p); else if (netif_is_bridge_master(dev)) @@ -1303,18 +1305,23 @@ static int __br_vlan_get_pvid(const stru *p_pvid = br_get_pvid(vg); return 0; } - -int br_vlan_get_pvid(const struct net_device *dev, u16 *p_pvid) -{ - ASSERT_RTNL(); - - return __br_vlan_get_pvid(dev, br_port_get_check_rtnl(dev), p_pvid); -} EXPORT_SYMBOL_GPL(br_vlan_get_pvid);
int br_vlan_get_pvid_rcu(const struct net_device *dev, u16 *p_pvid) { - return __br_vlan_get_pvid(dev, br_port_get_check_rcu(dev), p_pvid); + struct net_bridge_vlan_group *vg; + struct net_bridge_port *p; + + p = br_port_get_check_rcu(dev); + if (p) + vg = nbp_vlan_group_rcu(p); + else if (netif_is_bridge_master(dev)) + vg = br_vlan_group_rcu(netdev_priv(dev)); + else + return -EINVAL; + + *p_pvid = br_get_pvid(vg); + return 0; } EXPORT_SYMBOL_GPL(br_vlan_get_pvid_rcu);