net: Fix IP_MULTICAST_IF
ipv4/ipv6 setsockopt(IP_MULTICAST_IF) have dubious __dev_get_by_index() calls.
This function should be called only with RTNL or dev_base_lock held, or reader
could see a corrupt hash chain and eventually enter an endless loop.
Fix is to call dev_get_by_index()/dev_put().
If this happens to be performance critical, we could define a new dev_exist_by_index()
function to avoid touching dev refcount.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 14f54eb..4f7aaf6 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -496,13 +496,17 @@
goto e_inval;
if (val) {
+ struct net_device *dev;
+
if (sk->sk_bound_dev_if && sk->sk_bound_dev_if != val)
goto e_inval;
- if (__dev_get_by_index(net, val) == NULL) {
+ dev = dev_get_by_index(net, val);
+ if (!dev) {
retv = -ENODEV;
break;
}
+ dev_put(dev);
}
np->mcast_oif = val;
retv = 0;