* [PATCH v2] bridge: Fix possible races between assigning rx_handler_data and setting IFF_BRIDGE_PORT bit
@ 2021-04-28 14:38 zhangzhengming
2021-04-29 22:40 ` patchwork-bot+netdevbpf
0 siblings, 1 reply; 2+ messages in thread
From: zhangzhengming @ 2021-04-28 14:38 UTC (permalink / raw)
To: roopa, nikolay, davem, kuba
Cc: bridge, netdev, zhangzhengming, wangxiaogang3, xuhanbing
From: Zhang Zhengming <zhangzhengming@huawei.com>
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>
---
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 f2b1343..ed5aba2 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -103,8 +103,9 @@ 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);
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2] bridge: Fix possible races between assigning rx_handler_data and setting IFF_BRIDGE_PORT bit
2021-04-28 14:38 [PATCH v2] bridge: Fix possible races between assigning rx_handler_data and setting IFF_BRIDGE_PORT bit zhangzhengming
@ 2021-04-29 22:40 ` patchwork-bot+netdevbpf
0 siblings, 0 replies; 2+ messages in thread
From: patchwork-bot+netdevbpf @ 2021-04-29 22:40 UTC (permalink / raw)
To: zhangzhengming
Cc: roopa, nikolay, davem, kuba, bridge, netdev, wangxiaogang3, xuhanbing
Hello:
This patch was applied to netdev/net.git (refs/heads/master):
On Wed, 28 Apr 2021 22:38:14 +0800 you wrote:
> From: Zhang Zhengming <zhangzhengming@huawei.com>
>
> 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
>
> [...]
Here is the summary with links:
- [v2] bridge: Fix possible races between assigning rx_handler_data and setting IFF_BRIDGE_PORT bit
https://git.kernel.org/netdev/net/c/59259ff7a81b
You are awesome, thank you!
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