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

From: Hannes Frederic Sowa
Date: Mon Sep 01 2014 - 18:26:30 EST

Hi,

On Mo, 2014-09-01 at 23:05 +0200, Sabrina Dubroca wrote:
> 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@xxxxxxxxx>
> Signed-off-by: Sabrina Dubroca <sd@xxxxxxxxxxxxxxx>
> Reported-by: Tommi Rantala <tt.rantala@xxxxxxxxx>
> ---
> 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.

Ack, thus you should base the patch on the net tree.

>
> 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);

I don't have a very strong opinion on that, but think we shouldn't touch
this function. In general it looks like a useful one and if you force
rtnl lock on it you cannot call it from bh anymore. I think we should
keep rcu locking here and in the anycast code. It shouldn't matter much.

> /**
> * 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();

We would need to keep rcu_read_lock inside rtnl_lock if you decide to
keep dev_get_by_flags_rcu around.

> 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();

...here, too.

> 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();
> +

Minor nit:
This one is not necessary and will be guarded by the __ipv6_dev_mc_dec
one.

> rcu_read_lock();
>
> idev = __in6_dev_get(dev);

Rest looks good to me, thanks,
Hannes


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