Re: [PATCH] bonding: avoid adding slave device with IFF_MASTER flag
From: Eric Dumazet <hidden>
Date: 2021-06-22 17:53:09
On 6/22/21 5:09 AM, zhudi wrote:
quoted hunk ↗ jump to hunk
From: Di Zhu <redacted> The following steps will definitely cause the kernel to crash: ip link add vrf1 type vrf table 1 modprobe bonding.ko max_bonds=1 echo "+vrf1" >/sys/class/net/bond0/bonding/slaves rmmod bonding The root cause is that: When the VRF is added to the slave device, it will fail, and some cleaning work will be done. because VRF device has IFF_MASTER flag, cleanup process will not clear the IFF_BONDING flag. Then, when we unload the bonding module, unregister_netdevice_notifier() will treat the VRF device as a bond master device and treat netdev_priv() as struct bonding{} which actually is struct net_vrf{}. By analyzing the processing logic of bond_enslave(), it seems that it is not allowed to add the slave device with the IFF_MASTER flag, so we need to add a code check for this situation. Signed-off-by: Di Zhu <redacted> --- drivers/net/bonding/bond_main.c | 6 ++++++ 1 file changed, 6 insertions(+)diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c index c5a646d06102..16840c9bc00d 100644 --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c@@ -1601,6 +1601,12 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev, int link_reporting; int res = 0, i; + if (slave_dev->flags & IFF_MASTER) {
Missing NL_SET_ERR_MSG( ?
+ netdev_err(bond_dev,
+ "Error: Device with IFF_MASTER cannot be enslaved\n");
+ return -EPERM;
+ }
+
if (!bond->params.use_carrier &&
slave_dev->ethtool_ops->get_link == NULL &&
slave_ops->ndo_do_ioctl == NULL) {
This is strange, can you tell us why we keep the following lines after your patch ?
if (bond_dev == slave_dev) {
NL_SET_ERR_MSG(extack, "Cannot enslave bond to itself.");
netdev_err(bond_dev, "cannot enslave bond to itself.\n");
return -EPERM;
}
I was under the impression that a stack of bonding devices was allowed.