From: Zhang Zhengming zhangzhengming@huawei.com
[ Upstream commit 59259ff7a81b9eb6213891c6451221e567f8f22f ]
There is a crash in the function br_get_link_af_size_filtered, as the port_exists(dev) is true and the rx_handler_data of dev is NULL. But the rx_handler_data of dev is correct saved in vmcore.
The oops looks something like: ... pc : br_get_link_af_size_filtered+0x28/0x1c8 [bridge] ... Call trace: br_get_link_af_size_filtered+0x28/0x1c8 [bridge] if_nlmsg_size+0x180/0x1b0 rtnl_calcit.isra.12+0xf8/0x148 rtnetlink_rcv_msg+0x334/0x370 netlink_rcv_skb+0x64/0x130 rtnetlink_rcv+0x28/0x38 netlink_unicast+0x1f0/0x250 netlink_sendmsg+0x310/0x378 sock_sendmsg+0x4c/0x70 __sys_sendto+0x120/0x150 __arm64_sys_sendto+0x30/0x40 el0_svc_common+0x78/0x130 el0_svc_handler+0x38/0x78 el0_svc+0x8/0xc
In br_add_if(), we found there is no guarantee that assigning rx_handler_data to dev->rx_handler_data will before setting the IFF_BRIDGE_PORT bit of priv_flags. So there is a possible data competition:
CPU 0: CPU 1: (RCU read lock) (RTNL lock) rtnl_calcit() br_add_slave() if_nlmsg_size() br_add_if() br_get_link_af_size_filtered() -> netdev_rx_handler_register ... // The order is not guaranteed ... -> dev->priv_flags |= IFF_BRIDGE_PORT; // The IFF_BRIDGE_PORT bit of priv_flags has been set -> if (br_port_exists(dev)) { // The dev->rx_handler_data has NOT been assigned -> p = br_port_get_rcu(dev); .... -> rcu_assign_pointer(dev->rx_handler_data, rx_handler_data); ...
Fix it in br_get_link_af_size_filtered, using br_port_get_check_rcu() and checking the return value.
Signed-off-by: Zhang Zhengming zhangzhengming@huawei.com Reviewed-by: Zhao Lei zhaolei69@huawei.com Reviewed-by: Wang Xiaogang wangxiaogang3@huawei.com Suggested-by: Nikolay Aleksandrov nikolay@nvidia.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/bridge/br_netlink.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c index a0a54482aabc..8a664148f57a 100644 --- a/net/bridge/br_netlink.c +++ b/net/bridge/br_netlink.c @@ -99,8 +99,9 @@ static size_t br_get_link_af_size_filtered(const struct net_device *dev,
rcu_read_lock(); if (netif_is_bridge_port(dev)) { - p = br_port_get_rcu(dev); - vg = nbp_vlan_group_rcu(p); + p = br_port_get_check_rcu(dev); + if (p) + vg = nbp_vlan_group_rcu(p); } else if (dev->priv_flags & IFF_EBRIDGE) { br = netdev_priv(dev); vg = br_vlan_group_rcu(br);