From: Nikolay Aleksandrov <nikolay@xxxxxxxxxx>
Before commit ad2f99aedf8f ("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: syzbot+34fe5894623c4ab1b379@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: ad2f99aedf8f ("net: bridge: move bridge ioctls out of .ndo_do_ioctl")
Signed-off-by: Nikolay Aleksandrov <nikolay@xxxxxxxxxx>
---
net/bridge/br_if.c | 4 +---
net/bridge/br_ioctl.c | 37 ++++++++++++++++++++++++-------------
net/core/dev_ioctl.c | 7 ++++++-
3 files changed, 31 insertions(+), 17 deletions(-)
diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index 86f6d7e93ea8..67c60240b713 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -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;
}
diff --git a/net/bridge/br_ioctl.c b/net/bridge/br_ioctl.c
index 46a24c20e405..2f848de3e755 100644
--- a/net/bridge/br_ioctl.c
+++ b/net/bridge/br_ioctl.c
@@ -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;
}
diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index 4035bce06bf8..ff16326f5903 100644
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -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);
--
2.31.1
