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authorFrancesco Ruggeri <fruggeri@aristanetworks.com>2015-11-05 08:16:14 -0800
committerDavid S. Miller <davem@davemloft.net>2015-11-05 14:48:42 -0500
commit30f7ea1c2b5f5fb7462c5ae44fe2e40cb2d6a474 (patch)
tree47da4e1bb16c1115e634744ebd4b7a1659e47324 /net
parentf668f5f7e0861087ef9d64d473a9c1399fc25471 (diff)
packet: race condition in packet_bind
There is a race conditions between packet_notifier and packet_bind{_spkt}. It happens if packet_notifier(NETDEV_UNREGISTER) executes between the time packet_bind{_spkt} takes a reference on the new netdevice and the time packet_do_bind sets po->ifindex. In this case the notification can be missed. If this happens during a dev_change_net_namespace this can result in the netdevice to be moved to the new namespace while the packet_sock in the old namespace still holds a reference on it. When the netdevice is later deleted in the new namespace the deletion hangs since the packet_sock is not found in the new namespace' &net->packet.sklist. It can be reproduced with the script below. This patch makes packet_do_bind check again for the presence of the netdevice in the packet_sock's namespace after the synchronize_net in unregister_prot_hook. More in general it also uses the rcu lock for the duration of the bind to stop dev_change_net_namespace/rollback_registered_many from going past the synchronize_net following unlist_netdevice, so that no NETDEV_UNREGISTER notifications can happen on the new netdevice while the bind is executing. In order to do this some code from packet_bind{_spkt} is consolidated into packet_do_dev. import socket, os, time, sys proto=7 realDev='em1' vlanId=400 if len(sys.argv) > 1: vlanId=int(sys.argv[1]) dev='vlan%d' % vlanId os.system('taskset -p 0x10 %d' % os.getpid()) s = socket.socket(socket.PF_PACKET, socket.SOCK_RAW, proto) os.system('ip link add link %s name %s type vlan id %d' % (realDev, dev, vlanId)) os.system('ip netns add dummy') pid=os.fork() if pid == 0: # dev should be moved while packet_do_bind is in synchronize net os.system('taskset -p 0x20000 %d' % os.getpid()) os.system('ip link set %s netns dummy' % dev) os.system('ip netns exec dummy ip link del %s' % dev) s.close() sys.exit(0) time.sleep(.004) try: s.bind(('%s' % dev, proto+1)) except: print 'Could not bind socket' s.close() os.system('ip netns del dummy') sys.exit(0) os.waitpid(pid, 0) s.close() os.system('ip netns del dummy') sys.exit(0) Signed-off-by: Francesco Ruggeri <fruggeri@arista.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/packet/af_packet.c80
1 files changed, 49 insertions, 31 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 691660b9b7ef..af399cac5205 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2911,22 +2911,40 @@ static int packet_release(struct socket *sock)
* Attach a packet hook.
*/
-static int packet_do_bind(struct sock *sk, struct net_device *dev, __be16 proto)
+static int packet_do_bind(struct sock *sk, const char *name, int ifindex,
+ __be16 proto)
{
struct packet_sock *po = pkt_sk(sk);
struct net_device *dev_curr;
__be16 proto_curr;
bool need_rehook;
+ struct net_device *dev = NULL;
+ int ret = 0;
+ bool unlisted = false;
- if (po->fanout) {
- if (dev)
- dev_put(dev);
-
+ if (po->fanout)
return -EINVAL;
- }
lock_sock(sk);
spin_lock(&po->bind_lock);
+ rcu_read_lock();
+
+ if (name) {
+ dev = dev_get_by_name_rcu(sock_net(sk), name);
+ if (!dev) {
+ ret = -ENODEV;
+ goto out_unlock;
+ }
+ } else if (ifindex) {
+ dev = dev_get_by_index_rcu(sock_net(sk), ifindex);
+ if (!dev) {
+ ret = -ENODEV;
+ goto out_unlock;
+ }
+ }
+
+ if (dev)
+ dev_hold(dev);
proto_curr = po->prot_hook.type;
dev_curr = po->prot_hook.dev;
@@ -2934,14 +2952,29 @@ static int packet_do_bind(struct sock *sk, struct net_device *dev, __be16 proto)
need_rehook = proto_curr != proto || dev_curr != dev;
if (need_rehook) {
- unregister_prot_hook(sk, true);
+ if (po->running) {
+ rcu_read_unlock();
+ __unregister_prot_hook(sk, true);
+ rcu_read_lock();
+ dev_curr = po->prot_hook.dev;
+ if (dev)
+ unlisted = !dev_get_by_index_rcu(sock_net(sk),
+ dev->ifindex);
+ }
po->num = proto;
po->prot_hook.type = proto;
- po->prot_hook.dev = dev;
- po->ifindex = dev ? dev->ifindex : 0;
- packet_cached_dev_assign(po, dev);
+ if (unlikely(unlisted)) {
+ dev_put(dev);
+ po->prot_hook.dev = NULL;
+ po->ifindex = -1;
+ packet_cached_dev_reset(po);
+ } else {
+ po->prot_hook.dev = dev;
+ po->ifindex = dev ? dev->ifindex : 0;
+ packet_cached_dev_assign(po, dev);
+ }
}
if (dev_curr)
dev_put(dev_curr);
@@ -2949,7 +2982,7 @@ static int packet_do_bind(struct sock *sk, struct net_device *dev, __be16 proto)
if (proto == 0 || !need_rehook)
goto out_unlock;
- if (!dev || (dev->flags & IFF_UP)) {
+ if (!unlisted && (!dev || (dev->flags & IFF_UP))) {
register_prot_hook(sk);
} else {
sk->sk_err = ENETDOWN;
@@ -2958,9 +2991,10 @@ static int packet_do_bind(struct sock *sk, struct net_device *dev, __be16 proto)
}
out_unlock:
+ rcu_read_unlock();
spin_unlock(&po->bind_lock);
release_sock(sk);
- return 0;
+ return ret;
}
/*
@@ -2972,8 +3006,6 @@ static int packet_bind_spkt(struct socket *sock, struct sockaddr *uaddr,
{
struct sock *sk = sock->sk;
char name[15];
- struct net_device *dev;
- int err = -ENODEV;
/*
* Check legality
@@ -2983,19 +3015,13 @@ static int packet_bind_spkt(struct socket *sock, struct sockaddr *uaddr,
return -EINVAL;
strlcpy(name, uaddr->sa_data, sizeof(name));
- dev = dev_get_by_name(sock_net(sk), name);
- if (dev)
- err = packet_do_bind(sk, dev, pkt_sk(sk)->num);
- return err;
+ return packet_do_bind(sk, name, 0, pkt_sk(sk)->num);
}
static int packet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
struct sockaddr_ll *sll = (struct sockaddr_ll *)uaddr;
struct sock *sk = sock->sk;
- struct net_device *dev = NULL;
- int err;
-
/*
* Check legality
@@ -3006,16 +3032,8 @@ static int packet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len
if (sll->sll_family != AF_PACKET)
return -EINVAL;
- if (sll->sll_ifindex) {
- err = -ENODEV;
- dev = dev_get_by_index(sock_net(sk), sll->sll_ifindex);
- if (dev == NULL)
- goto out;
- }
- err = packet_do_bind(sk, dev, sll->sll_protocol ? : pkt_sk(sk)->num);
-
-out:
- return err;
+ return packet_do_bind(sk, NULL, sll->sll_ifindex,
+ sll->sll_protocol ? : pkt_sk(sk)->num);
}
static struct proto packet_proto = {