net: arp_ioctl() must hold RTNL

Commit 941666c2e3e0 "net: RCU conversion of dev_getbyhwaddr() and
arp_ioctl()" introduced a regression, reported by Jamie Heilman.
"arp -Ds 192.168.2.41 eth0 pub" triggered the ASSERT_RTNL() assert
in pneigh_lookup()

Removing RTNL requirement from arp_ioctl() was a mistake, just revert
that part.

Reported-by: Jamie Heilman <jamie@audible.transient.net>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/dev.c b/net/core/dev.c
index 8393ec4..1e5077d 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -749,7 +749,8 @@ EXPORT_SYMBOL(dev_get_by_index);
  *     @ha: hardware address
  *
  *     Search for an interface by MAC address. Returns NULL if the device
- *     is not found or a pointer to the device. The caller must hold RCU
+ *     is not found or a pointer to the device.
+ *     The caller must hold RCU or RTNL.
  *     The returned device has not had its ref count increased
  *     and the caller must therefore be careful about locking
  *

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 04c8b69..7927589 100644 (file)
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1017,14 +1017,13 @@ static int arp_req_set_proxy(struct net *net, struct net_device *dev, int on)
                IPV4_DEVCONF_ALL(net, PROXY_ARP) = on;
                return 0;
        }
-       if (__in_dev_get_rcu(dev)) {
-               IN_DEV_CONF_SET(__in_dev_get_rcu(dev), PROXY_ARP, on);
+       if (__in_dev_get_rtnl(dev)) {
+               IN_DEV_CONF_SET(__in_dev_get_rtnl(dev), PROXY_ARP, on);
                return 0;
        }
        return -ENXIO;
 }
 
-/* must be called with rcu_read_lock() */
 static int arp_req_set_public(struct net *net, struct arpreq *r,
                struct net_device *dev)
 {
@@ -1233,10 +1232,10 @@ int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
        if (!(r.arp_flags & ATF_NETMASK))
                ((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr =
                                                           htonl(0xFFFFFFFFUL);
-       rcu_read_lock();
+       rtnl_lock();
        if (r.arp_dev[0]) {
                err = -ENODEV;
-               dev = dev_get_by_name_rcu(net, r.arp_dev);
+               dev = __dev_get_by_name(net, r.arp_dev);
                if (dev == NULL)
                        goto out;
 
@@ -1263,7 +1262,7 @@ int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
                break;
        }
 out:
-       rcu_read_unlock();
+       rtnl_unlock();
        if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
                err = -EFAULT;
        return err;