[PATCH] ipv6: fix rtnl locking in setsockopt for anycast and multicast

[Sabrina Dubroca <sd@queasysnail.net>]

Calling setsockopt with IPV6_JOIN_ANYCAST or IPV6_LEAVE_ANYCAST
triggers the assertion in addrconf_join_solict()/addrconf_leave_solict()

ipv6_sock_ac_join(), ipv6_sock_ac_drop(), ipv6_sock_ac_close() need to
take RTNL before calling ipv6_dev_ac_inc/dec. Same thing with
ipv6_sock_mc_join(), ipv6_sock_mc_drop(), ipv6_sock_mc_close() before
calling ipv6_dev_mc_inc/dec.

This patch moves ASSERT_RTNL() up a level in the call stack.

Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reported-by: Tommi Rantala <tt.rantala@gmail.com>
---
I included Cong's Signed-off-by for the first part of the patch,
I hope that's OK.

This patch is based on -next, but since the assertion can also be
triggered on a current kernel (tested on a 3.16), I think it should
also go in stable.

 include/linux/netdevice.h |  4 ++--
 net/core/dev.c            | 11 ++++++-----
 net/ipv6/addrconf.c       | 15 +++++----------
 net/ipv6/anycast.c        | 30 +++++++++++++++++++-----------
 net/ipv6/mcast.c          | 16 ++++++++++++++++
 5 files changed, 48 insertions(+), 28 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 429801370d0c..1ae0e745b1b1 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2077,8 +2077,8 @@ void __dev_remove_pack(struct packet_type *pt);
 void dev_add_offload(struct packet_offload *po);
 void dev_remove_offload(struct packet_offload *po);
 
-struct net_device *dev_get_by_flags_rcu(struct net *net, unsigned short flags,
-					unsigned short mask);
+struct net_device *dev_get_by_flags(struct net *net, unsigned short flags,
+				    unsigned short mask);
 struct net_device *dev_get_by_name(struct net *net, const char *name);
 struct net_device *dev_get_by_name_rcu(struct net *net, const char *name);
 struct net_device *__dev_get_by_name(struct net *net, const char *name);
diff --git a/net/core/dev.c b/net/core/dev.c
index 443b814db05b..8fede6ef4a39 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -897,23 +897,24 @@ struct net_device *dev_getfirstbyhwtype(struct net *net, unsigned short type)
 EXPORT_SYMBOL(dev_getfirstbyhwtype);
 
 /**
- *	dev_get_by_flags_rcu - find any device with given flags
+ *	dev_get_by_flags - find any device with given flags
  *	@net: the applicable net namespace
  *	@if_flags: IFF_* values
  *	@mask: bitmask of bits in if_flags to check
  *
  *	Search for any interface with the given flags. Returns NULL if a device
  *	is not found or a pointer to the device. Must be called inside
- *	rcu_read_lock(), and result refcount is unchanged.
+ *	rtnl_lock(), and result refcount is unchanged.
  */
 
-struct net_device *dev_get_by_flags_rcu(struct net *net, unsigned short if_flags,
+struct net_device *dev_get_by_flags(struct net *net, unsigned short if_flags,
 				    unsigned short mask)
 {
 	struct net_device *dev, *ret;
 
+	ASSERT_RTNL();
 	ret = NULL;
-	for_each_netdev_rcu(net, dev) {
+	for_each_netdev(net, dev) {
 		if (((dev->flags ^ if_flags) & mask) == 0) {
 			ret = dev;
 			break;
@@ -921,7 +922,7 @@ struct net_device *dev_get_by_flags_rcu(struct net *net, unsigned short if_flags
 	}
 	return ret;
 }
-EXPORT_SYMBOL(dev_get_by_flags_rcu);
+EXPORT_SYMBOL(dev_get_by_flags);
 
 /**
  *	dev_valid_name - check if name is okay for network device
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 267ce3caee24..7ada65937d23 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1690,14 +1690,12 @@ void addrconf_dad_failure(struct inet6_ifaddr *ifp)
 	addrconf_mod_dad_work(ifp, 0);
 }
 
-/* Join to solicited addr multicast group. */
-
+/* Join to solicited addr multicast group.
+ * caller must hold RTNL */
 void addrconf_join_solict(struct net_device *dev, const struct in6_addr *addr)
 {
 	struct in6_addr maddr;
 
-	ASSERT_RTNL();
-
 	if (dev->flags&(IFF_LOOPBACK|IFF_NOARP))
 		return;
 
@@ -1705,12 +1703,11 @@ void addrconf_join_solict(struct net_device *dev, const struct in6_addr *addr)
 	ipv6_dev_mc_inc(dev, &maddr);
 }
 
+/* caller must hold RTNL */
 void addrconf_leave_solict(struct inet6_dev *idev, const struct in6_addr *addr)
 {
 	struct in6_addr maddr;
 
-	ASSERT_RTNL();
-
 	if (idev->dev->flags&(IFF_LOOPBACK|IFF_NOARP))
 		return;
 
@@ -1718,12 +1715,11 @@ void addrconf_leave_solict(struct inet6_dev *idev, const struct in6_addr *addr)
 	__ipv6_dev_mc_dec(idev, &maddr);
 }
 
+/* caller must hold RTNL */
 static void addrconf_join_anycast(struct inet6_ifaddr *ifp)
 {
 	struct in6_addr addr;
 
-	ASSERT_RTNL();
-
 	if (ifp->prefix_len >= 127) /* RFC 6164 */
 		return;
 	ipv6_addr_prefix(&addr, &ifp->addr, ifp->prefix_len);
@@ -1732,12 +1728,11 @@ static void addrconf_join_anycast(struct inet6_ifaddr *ifp)
 	ipv6_dev_ac_inc(ifp->idev->dev, &addr);
 }
 
+/* caller must hold RTNL */
 static void addrconf_leave_anycast(struct inet6_ifaddr *ifp)
 {
 	struct in6_addr addr;
 
-	ASSERT_RTNL();
-
 	if (ifp->prefix_len >= 127) /* RFC 6164 */
 		return;
 	ipv6_addr_prefix(&addr, &ifp->addr, ifp->prefix_len);
diff --git a/net/ipv6/anycast.c b/net/ipv6/anycast.c
index 210183244689..572c2faede55 100644
--- a/net/ipv6/anycast.c
+++ b/net/ipv6/anycast.c
@@ -77,7 +77,7 @@ int ipv6_sock_ac_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 	pac->acl_next = NULL;
 	pac->acl_addr = *addr;
 
-	rcu_read_lock();
+	rtnl_lock();
 	if (ifindex == 0) {
 		struct rt6_info *rt;
 
@@ -90,11 +90,11 @@ int ipv6_sock_ac_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 			goto error;
 		} else {
 			/* router, no matching interface: just pick one */
-			dev = dev_get_by_flags_rcu(net, IFF_UP,
-						   IFF_UP | IFF_LOOPBACK);
+			dev = dev_get_by_flags(net, IFF_UP,
+					       IFF_UP | IFF_LOOPBACK);
 		}
 	} else
-		dev = dev_get_by_index_rcu(net, ifindex);
+		dev = __dev_get_by_index(net, ifindex);
 
 	if (dev == NULL) {
 		err = -ENODEV;
@@ -136,7 +136,7 @@ int ipv6_sock_ac_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 	}
 
 error:
-	rcu_read_unlock();
+	rtnl_unlock();
 	if (pac)
 		sock_kfree_s(sk, pac, sizeof(*pac));
 	return err;
@@ -171,13 +171,15 @@ int ipv6_sock_ac_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
 
 	spin_unlock_bh(&ipv6_sk_ac_lock);
 
-	rcu_read_lock();
-	dev = dev_get_by_index_rcu(net, pac->acl_ifindex);
+	rtnl_lock();
+	dev = __dev_get_by_index(net, pac->acl_ifindex);
 	if (dev)
 		ipv6_dev_ac_dec(dev, &pac->acl_addr);
-	rcu_read_unlock();
+	rtnl_unlock();
 
 	sock_kfree_s(sk, pac, sizeof(*pac));
+	if (!dev)
+		return -ENODEV;
 	return 0;
 }
 
@@ -198,12 +200,12 @@ void ipv6_sock_ac_close(struct sock *sk)
 	spin_unlock_bh(&ipv6_sk_ac_lock);
 
 	prev_index = 0;
-	rcu_read_lock();
+	rtnl_lock();
 	while (pac) {
 		struct ipv6_ac_socklist *next = pac->acl_next;
 
 		if (pac->acl_ifindex != prev_index) {
-			dev = dev_get_by_index_rcu(net, pac->acl_ifindex);
+			dev = __dev_get_by_index(net, pac->acl_ifindex);
 			prev_index = pac->acl_ifindex;
 		}
 		if (dev)
@@ -211,7 +213,7 @@ void ipv6_sock_ac_close(struct sock *sk)
 		sock_kfree_s(sk, pac, sizeof(*pac));
 		pac = next;
 	}
-	rcu_read_unlock();
+	rtnl_unlock();
 }
 
 static void aca_put(struct ifacaddr6 *ac)
@@ -233,6 +235,8 @@ int ipv6_dev_ac_inc(struct net_device *dev, const struct in6_addr *addr)
 	struct rt6_info *rt;
 	int err;
 
+	ASSERT_RTNL();
+
 	idev = in6_dev_get(dev);
 
 	if (idev == NULL)
@@ -302,6 +306,8 @@ int __ipv6_dev_ac_dec(struct inet6_dev *idev, const struct in6_addr *addr)
 {
 	struct ifacaddr6 *aca, *prev_aca;
 
+	ASSERT_RTNL();
+
 	write_lock_bh(&idev->lock);
 	prev_aca = NULL;
 	for (aca = idev->ac_list; aca; aca = aca->aca_next) {
@@ -336,6 +342,8 @@ static int ipv6_dev_ac_dec(struct net_device *dev, const struct in6_addr *addr)
 {
 	struct inet6_dev *idev = __in6_dev_get(dev);
 
+	ASSERT_RTNL();
+
 	if (idev == NULL)
 		return -ENODEV;
 	return __ipv6_dev_ac_dec(idev, addr);
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 70881795da96..d73ac1ef65f2 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -172,6 +172,7 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 	mc_lst->next = NULL;
 	mc_lst->addr = *addr;
 
+	rtnl_lock();
 	rcu_read_lock();
 	if (ifindex == 0) {
 		struct rt6_info *rt;
@@ -185,6 +186,7 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 
 	if (dev == NULL) {
 		rcu_read_unlock();
+		rtnl_unlock();
 		sock_kfree_s(sk, mc_lst, sizeof(*mc_lst));
 		return -ENODEV;
 	}
@@ -202,6 +204,7 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 
 	if (err) {
 		rcu_read_unlock();
+		rtnl_unlock();
 		sock_kfree_s(sk, mc_lst, sizeof(*mc_lst));
 		return err;
 	}
@@ -212,6 +215,7 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
 	spin_unlock(&ipv6_sk_mc_lock);
 
 	rcu_read_unlock();
+	rtnl_unlock();
 
 	return 0;
 }
@@ -229,6 +233,7 @@ int ipv6_sock_mc_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
 	if (!ipv6_addr_is_multicast(addr))
 		return -EINVAL;
 
+	rtnl_lock();
 	spin_lock(&ipv6_sk_mc_lock);
 	for (lnk = &np->ipv6_mc_list;
 	     (mc_lst = rcu_dereference_protected(*lnk,
@@ -252,12 +257,15 @@ int ipv6_sock_mc_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
 			} else
 				(void) ip6_mc_leave_src(sk, mc_lst, NULL);
 			rcu_read_unlock();
+			rtnl_unlock();
+
 			atomic_sub(sizeof(*mc_lst), &sk->sk_omem_alloc);
 			kfree_rcu(mc_lst, rcu);
 			return 0;
 		}
 	}
 	spin_unlock(&ipv6_sk_mc_lock);
+	rtnl_unlock();
 
 	return -EADDRNOTAVAIL;
 }
@@ -302,6 +310,7 @@ void ipv6_sock_mc_close(struct sock *sk)
 	if (!rcu_access_pointer(np->ipv6_mc_list))
 		return;
 
+	rtnl_lock();
 	spin_lock(&ipv6_sk_mc_lock);
 	while ((mc_lst = rcu_dereference_protected(np->ipv6_mc_list,
 				lockdep_is_held(&ipv6_sk_mc_lock))) != NULL) {
@@ -328,6 +337,7 @@ void ipv6_sock_mc_close(struct sock *sk)
 		spin_lock(&ipv6_sk_mc_lock);
 	}
 	spin_unlock(&ipv6_sk_mc_lock);
+	rtnl_unlock();
 }
 
 int ip6_mc_source(int add, int omode, struct sock *sk,
@@ -845,6 +855,8 @@ int ipv6_dev_mc_inc(struct net_device *dev, const struct in6_addr *addr)
 	struct ifmcaddr6 *mc;
 	struct inet6_dev *idev;
 
+	ASSERT_RTNL();
+
 	/* we need to take a reference on idev */
 	idev = in6_dev_get(dev);
 
@@ -916,6 +928,8 @@ int __ipv6_dev_mc_dec(struct inet6_dev *idev, const struct in6_addr *addr)
 {
 	struct ifmcaddr6 *ma, **map;
 
+	ASSERT_RTNL();
+
 	write_lock_bh(&idev->lock);
 	for (map = &idev->mc_list; (ma = *map) != NULL; map = &ma->next) {
 		if (ipv6_addr_equal(&ma->mca_addr, addr)) {
@@ -942,6 +956,8 @@ int ipv6_dev_mc_dec(struct net_device *dev, const struct in6_addr *addr)
 	struct inet6_dev *idev;
 	int err;
 
+	ASSERT_RTNL();
+
 	rcu_read_lock();
 
 	idev = __in6_dev_get(dev);
-- 
2.1.0