[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20210512180408.665338-17-sashal@kernel.org>
Date: Wed, 12 May 2021 14:04:01 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Zhang Zhengming <zhangzhengming@...wei.com>,
Zhao Lei <zhaolei69@...wei.com>,
Wang Xiaogang <wangxiaogang3@...wei.com>,
Nikolay Aleksandrov <nikolay@...dia.com>,
"David S . Miller" <davem@...emloft.net>,
Sasha Levin <sashal@...nel.org>,
bridge@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 17/23] bridge: Fix possible races between assigning rx_handler_data and setting IFF_BRIDGE_PORT bit
From: Zhang Zhengming <zhangzhengming@...wei.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@...wei.com>
Reviewed-by: Zhao Lei <zhaolei69@...wei.com>
Reviewed-by: Wang Xiaogang <wangxiaogang3@...wei.com>
Suggested-by: Nikolay Aleksandrov <nikolay@...dia.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.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);
--
2.30.2
Powered by blists - more mailing lists