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/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 0c0b6e3..e982b5c 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -634,17 +634,16 @@
break;
}
dev = ip_dev_find(sock_net(sk), mreq.imr_address.s_addr);
- if (dev) {
+ if (dev)
mreq.imr_ifindex = dev->ifindex;
- dev_put(dev);
- }
} else
- dev = __dev_get_by_index(sock_net(sk), mreq.imr_ifindex);
+ dev = dev_get_by_index(sock_net(sk), mreq.imr_ifindex);
err = -EADDRNOTAVAIL;
if (!dev)
break;
+ dev_put(dev);
err = -EINVAL;
if (sk->sk_bound_dev_if &&