net: RCU conversion of dev_getbyhwaddr() and arp_ioctl()

Le dimanche 05 décembre 2010 à 09:19 +0100, Eric Dumazet a écrit :

> Hmm..
>
> If somebody can explain why RTNL is held in arp_ioctl() (and therefore
> in arp_req_delete()), we might first remove RTNL use in arp_ioctl() so
> that your patch can be applied.
>
> Right now it is not good, because RTNL wont be necessarly held when you
> are going to call arp_invalidate() ?

While doing this analysis, I found a refcount bug in llc, I'll send a
patch for net-2.6

Meanwhile, here is the patch for net-next-2.6

Your patch then can be applied after mine.

Thanks

[PATCH] net: RCU conversion of dev_getbyhwaddr() and arp_ioctl()

dev_getbyhwaddr() was called under RTNL.

Rename it to dev_getbyhwaddr_rcu() and change all its caller to now use
RCU locking instead of RTNL.

Change arp_ioctl() to use RCU instead of RTNL locking.

Note: this fix a dev refcount bug in llc

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 27 insertions, 27 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index a9ac5dc26e3c..d31bc3c94717 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1360,7 +1360,8 @@ static inline struct net_device *first_net_device(struct net *net)
 
 extern int                      netdev_boot_setup_check(struct net_device *dev);
 extern unsigned long            netdev_boot_base(const char *prefix, int unit);
-extern struct net_device    *dev_getbyhwaddr(struct net *net, unsigned short type, char *hwaddr);
+extern struct net_device *dev_getbyhwaddr_rcu(struct net *net, unsigned short type,
+                                              const char *hwaddr);
 extern struct net_device *dev_getfirstbyhwtype(struct net *net, unsigned short type);
 extern struct net_device *__dev_getfirstbyhwtype(struct net *net, unsigned short type);
 extern void             dev_add_pack(struct packet_type *pt);
diff --git a/net/core/dev.c b/net/core/dev.c
index ee605c0867e7..822b15b8d11c 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -743,34 +743,31 @@ struct net_device *dev_get_by_index(struct net *net, int ifindex)
 EXPORT_SYMBOL(dev_get_by_index);
 
 /**
- *      dev_getbyhwaddr - find a device by its hardware address
+ *      dev_getbyhwaddr_rcu - find a device by its hardware address
  *      @net: the applicable net namespace
  *      @type: media type of device
  *      @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 the
- *      rtnl semaphore. The returned device has not had its ref count increased
+ *      is not found or a pointer to the device. The caller must hold RCU
+ *      The returned device has not had its ref count increased
  *      and the caller must therefore be careful about locking
  *
- *      BUGS:
- *      If the API was consistent this would be __dev_get_by_hwaddr
  */
 
-struct net_device *dev_getbyhwaddr(struct net *net, unsigned short type, char *ha)
+struct net_device *dev_getbyhwaddr_rcu(struct net *net, unsigned short type,
+                                       const char *ha)
 {
         struct net_device *dev;
 
-        ASSERT_RTNL();
-
-        for_each_netdev(net, dev)
+        for_each_netdev_rcu(net, dev)
                 if (dev->type == type &&
                     !memcmp(dev->dev_addr, ha, dev->addr_len))
                         return dev;
 
         return NULL;
 }
-EXPORT_SYMBOL(dev_getbyhwaddr);
+EXPORT_SYMBOL(dev_getbyhwaddr_rcu);
 
 struct net_device *__dev_getfirstbyhwtype(struct net *net, unsigned short type)
 {
diff --git a/net/ieee802154/af_ieee802154.c b/net/ieee802154/af_ieee802154.c
index 93c91b633a56..6df6ecf49708 100644
--- a/net/ieee802154/af_ieee802154.c
+++ b/net/ieee802154/af_ieee802154.c
@@ -52,11 +52,11 @@ struct net_device *ieee802154_get_dev(struct net *net,
 
         switch (addr->addr_type) {
         case IEEE802154_ADDR_LONG:
-                rtnl_lock();
-                dev = dev_getbyhwaddr(net, ARPHRD_IEEE802154, addr->hwaddr);
+                rcu_read_lock();
+                dev = dev_getbyhwaddr_rcu(net, ARPHRD_IEEE802154, addr->hwaddr);
                 if (dev)
                         dev_hold(dev);
-                rtnl_unlock();
+                rcu_read_unlock();
                 break;
         case IEEE802154_ADDR_SHORT:
                 if (addr->pan_id == 0xffff ||
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 10af759f2630..a2fc7b961dbc 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1017,13 +1017,14 @@ 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_rtnl(dev)) {
-                IN_DEV_CONF_SET(__in_dev_get_rtnl(dev), PROXY_ARP, on);
+        if (__in_dev_get_rcu(dev)) {
+                IN_DEV_CONF_SET(__in_dev_get_rcu(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)
 {
@@ -1033,7 +1034,7 @@ static int arp_req_set_public(struct net *net, struct arpreq *r,
         if (mask && mask != htonl(0xFFFFFFFF))
                 return -EINVAL;
         if (!dev && (r->arp_flags & ATF_COM)) {
-                dev = dev_getbyhwaddr(net, r->arp_ha.sa_family,
+                dev = dev_getbyhwaddr_rcu(net, r->arp_ha.sa_family,
                                       r->arp_ha.sa_data);
                 if (!dev)
                         return -ENODEV;
@@ -1225,10 +1226,10 @@ 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);
-        rtnl_lock();
+        rcu_read_lock();
         if (r.arp_dev[0]) {
                 err = -ENODEV;
-                dev = __dev_get_by_name(net, r.arp_dev);
+                dev = dev_get_by_name_rcu(net, r.arp_dev);
                 if (dev == NULL)
                         goto out;
 
@@ -1252,12 +1253,12 @@ int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
                 break;
         case SIOCGARP:
                 err = arp_req_get(&r, dev);
-                if (!err && copy_to_user(arg, &r, sizeof(r)))
-                        err = -EFAULT;
                 break;
         }
 out:
-        rtnl_unlock();
+        rcu_read_unlock();
+        if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
+                err = -EFAULT;
         return err;
 }
 
diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 582612998211..dfd3a648a551 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -316,9 +316,9 @@ static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen)
         if (unlikely(addr->sllc_family != AF_LLC))
                 goto out;
         rc = -ENODEV;
-        rtnl_lock();
+        rcu_read_lock();
         if (sk->sk_bound_dev_if) {
-                llc->dev = dev_get_by_index(&init_net, sk->sk_bound_dev_if);
+                llc->dev = dev_get_by_index_rcu(&init_net, sk->sk_bound_dev_if);
                 if (llc->dev) {
                         if (!addr->sllc_arphrd)
                                 addr->sllc_arphrd = llc->dev->type;
@@ -329,14 +329,15 @@ static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen)
                             !llc_mac_match(addr->sllc_mac,
                                            llc->dev->dev_addr)) {
                                 rc = -EINVAL;
-                                dev_put(llc->dev);
                                 llc->dev = NULL;
                         }
                 }
         } else
-                llc->dev = dev_getbyhwaddr(&init_net, addr->sllc_arphrd,
+                llc->dev = dev_getbyhwaddr_rcu(&init_net, addr->sllc_arphrd,
                                            addr->sllc_mac);
-        rtnl_unlock();
+        if (llc->dev)
+                dev_hold(llc->dev);
+        rcu_read_unlock();
         if (!llc->dev)
                 goto out;
         if (!addr->sllc_sap) {