Commit 893b1958 authored by Nikolay Aleksandrov's avatar Nikolay Aleksandrov Committed by David S. Miller
Browse files

net: bridge: fix ioctl locking 



Before commit ad2f99ae ("net: bridge: move bridge ioctls out of
.ndo_do_ioctl") the bridge ioctl calls were divided in two parts:
one was deviceless called by sock_ioctl and didn't expect rtnl to be held,
the other was with a device called by dev_ifsioc() and expected rtnl to be
held. After the commit above they were united in a single ioctl stub, but
it didn't take care of the locking expectations.
For sock_ioctl now we acquire  (1) br_ioctl_mutex, (2) rtnl
and for dev_ifsioc we acquire  (1) rtnl,           (2) br_ioctl_mutex

The fix is to get a refcnt on the netdev for dev_ifsioc calls and drop rtnl
then to reacquire it in the bridge ioctl stub after br_ioctl_mutex has
been acquired. That will avoid playing locking games and make the rules
straight-forward: we always take br_ioctl_mutex first, and then rtnl.

Reported-by: default avatar <syzbot+34fe5894623c4ab1b379@syzkaller.appspotmail.com>
Fixes: ad2f99ae ("net: bridge: move bridge ioctls out of .ndo_do_ioctl")
Signed-off-by: default avatarNikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4167a960

net/bridge/br_if.c

+1 −3
Original line number Diff line number Diff line
@@ -456,7 +456,7 @@ int br_add_bridge(struct net *net, const char *name) 
	dev_net_set(dev, net);

	dev->rtnl_link_ops = &br_link_ops;



	res = register_netdev(dev);

	res = register_netdevice(dev);

	if (res)

		free_netdev(dev);

	return res;
@@ -467,7 +467,6 @@ int br_del_bridge(struct net *net, const char *name) 
	struct net_device *dev;

	int ret = 0;



	rtnl_lock();

	dev = __dev_get_by_name(net, name);

	if (dev == NULL)

		ret =  -ENXIO; 	/* Could not find device */
@@ -485,7 +484,6 @@ int br_del_bridge(struct net *net, const char *name) 
	else

		br_dev_delete(dev, NULL);



	rtnl_unlock();

	return ret;

}

net/bridge/br_ioctl.c

+24 −13
Original line number Diff line number Diff line
@@ -369,33 +369,44 @@ static int old_deviceless(struct net *net, void __user *uarg) 
int br_ioctl_stub(struct net *net, struct net_bridge *br, unsigned int cmd,

		  struct ifreq *ifr, void __user *uarg)

{

	int ret = -EOPNOTSUPP;



	rtnl_lock();



	switch (cmd) {

	case SIOCGIFBR:

	case SIOCSIFBR:

		return old_deviceless(net, uarg);



		ret = old_deviceless(net, uarg);

		break;

	case SIOCBRADDBR:

	case SIOCBRDELBR:

	{

		char buf[IFNAMSIZ];



		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))

			return -EPERM;

		if (!ns_capable(net->user_ns, CAP_NET_ADMIN)) {

			ret = -EPERM;

			break;

		}



		if (copy_from_user(buf, uarg, IFNAMSIZ))

			return -EFAULT;

		if (copy_from_user(buf, uarg, IFNAMSIZ)) {

			ret = -EFAULT;

			break;

		}



		buf[IFNAMSIZ-1] = 0;

		if (cmd == SIOCBRADDBR)

			return br_add_bridge(net, buf);



		return br_del_bridge(net, buf);

			ret = br_add_bridge(net, buf);

		else

			ret = br_del_bridge(net, buf);

	}



		break;

	case SIOCBRADDIF:

	case SIOCBRDELIF:

		return add_del_if(br, ifr->ifr_ifindex, cmd == SIOCBRADDIF);



		ret = add_del_if(br, ifr->ifr_ifindex, cmd == SIOCBRADDIF);

		break;

	}

	return -EOPNOTSUPP;



	rtnl_unlock();



	return ret;

}

net/core/dev_ioctl.c

+6 −1
Original line number Diff line number Diff line
@@ -379,7 +379,12 @@ static int dev_ifsioc(struct net *net, struct ifreq *ifr, void __user *data, 
	case SIOCBRDELIF:

		if (!netif_device_present(dev))

			return -ENODEV;

		return br_ioctl_call(net, netdev_priv(dev), cmd, ifr, NULL);

		dev_hold(dev);

		rtnl_unlock();

		err = br_ioctl_call(net, netdev_priv(dev), cmd, ifr, NULL);

		dev_put(dev);

		rtnl_lock();

		return err;



	case SIOCSHWTSTAMP:

		err = net_hwtstamp_validate(ifr);