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Date: Thu, 23 Aug 2012 01:16:51 -0700
From: ebiederm@...ssion.com (Eric W. Biederman)
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: David Miller <davem@...emloft.net>, gaofeng@...fujitsu.com,
netdev@...r.kernel.org, therbert@...gle.com, maheshb@...gle.com
Subject: Re: [PATCH net-next] net: reinstate rtnl in call_netdevice_notifiers()
Eric Dumazet <eric.dumazet@...il.com> writes:
> From: Eric Dumazet <edumazet@...gle.com>
>
> Eric Biederman pointed out that not holding RTNL while calling
> call_netdevice_notifiers() was racy.
>
> This patch is a direct transcription his feedback
> against commit 0115e8e30d6fc (net: remove delay at device dismantle)
>
> Thanks Eric !
Looks good to me.
Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Tom Herbert <therbert@...gle.com>
> Cc: Mahesh Bandewar <maheshb@...gle.com>
> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
> Cc: Gao feng <gaofeng@...fujitsu.com>
> ---
> Note: After this patch, it seems less risky to push these fixes for 3.6,
> since notifiers have the guarantee that RTNL is held.
>
> net/core/dev.c | 9 +++++++--
> net/core/fib_rules.c | 3 +--
> net/ipv4/devinet.c | 6 +-----
> net/ipv4/fib_frontend.c | 7 ++-----
> net/ipv6/addrconf.c | 6 +-----
> 5 files changed, 12 insertions(+), 19 deletions(-)
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 0640d2a..bc857fe 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -1466,8 +1466,7 @@ EXPORT_SYMBOL(unregister_netdevice_notifier);
>
> int call_netdevice_notifiers(unsigned long val, struct net_device *dev)
> {
> - if (val != NETDEV_UNREGISTER_FINAL)
> - ASSERT_RTNL();
> + ASSERT_RTNL();
> return raw_notifier_call_chain(&netdev_chain, val, dev);
> }
> EXPORT_SYMBOL(call_netdevice_notifiers);
> @@ -5782,7 +5781,11 @@ static void netdev_wait_allrefs(struct net_device *dev)
>
> /* Rebroadcast unregister notification */
> call_netdevice_notifiers(NETDEV_UNREGISTER, dev);
> +
> + __rtnl_unlock();
> rcu_barrier();
> + rtnl_lock();
> +
> call_netdevice_notifiers(NETDEV_UNREGISTER_FINAL, dev);
> if (test_bit(__LINK_STATE_LINKWATCH_PENDING,
> &dev->state)) {
> @@ -5855,7 +5858,9 @@ void netdev_run_todo(void)
> = list_first_entry(&list, struct net_device, todo_list);
> list_del(&dev->todo_list);
>
> + rtnl_lock();
> call_netdevice_notifiers(NETDEV_UNREGISTER_FINAL, dev);
> + __rtnl_unlock();
>
> if (unlikely(dev->reg_state != NETREG_UNREGISTERING)) {
> pr_err("network todo '%s' but state %d\n",
> diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
> index 5850937..ab7db83 100644
> --- a/net/core/fib_rules.c
> +++ b/net/core/fib_rules.c
> @@ -711,16 +711,15 @@ static int fib_rules_event(struct notifier_block *this, unsigned long event,
> struct net *net = dev_net(dev);
> struct fib_rules_ops *ops;
>
> + ASSERT_RTNL();
>
> switch (event) {
> case NETDEV_REGISTER:
> - ASSERT_RTNL();
> list_for_each_entry(ops, &net->rules_ops, list)
> attach_rules(&ops->rules_list, dev);
> break;
>
> case NETDEV_UNREGISTER:
> - ASSERT_RTNL();
> list_for_each_entry(ops, &net->rules_ops, list)
> detach_rules(&ops->rules_list, dev);
> break;
> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index 6a5e6e4..adf273f 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -1147,12 +1147,8 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
> void *ptr)
> {
> struct net_device *dev = ptr;
> - struct in_device *in_dev;
> -
> - if (event == NETDEV_UNREGISTER_FINAL)
> - goto out;
> + struct in_device *in_dev = __in_dev_get_rtnl(dev);
>
> - in_dev = __in_dev_get_rtnl(dev);
> ASSERT_RTNL();
>
> if (!in_dev) {
> diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
> index fd7d9ae..acdee32 100644
> --- a/net/ipv4/fib_frontend.c
> +++ b/net/ipv4/fib_frontend.c
> @@ -1050,9 +1050,6 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
> return NOTIFY_DONE;
> }
>
> - if (event == NETDEV_UNREGISTER_FINAL)
> - return NOTIFY_DONE;
> -
> in_dev = __in_dev_get_rtnl(dev);
>
> switch (event) {
> @@ -1064,14 +1061,14 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
> fib_sync_up(dev);
> #endif
> atomic_inc(&net->ipv4.dev_addr_genid);
> - rt_cache_flush(dev_net(dev), -1);
> + rt_cache_flush(net, -1);
> break;
> case NETDEV_DOWN:
> fib_disable_ip(dev, 0, 0);
> break;
> case NETDEV_CHANGEMTU:
> case NETDEV_CHANGE:
> - rt_cache_flush(dev_net(dev), 0);
> + rt_cache_flush(net, 0);
> break;
> }
> return NOTIFY_DONE;
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index e581009..6bc85f7 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -2566,14 +2566,10 @@ static int addrconf_notify(struct notifier_block *this, unsigned long event,
> void *data)
> {
> struct net_device *dev = (struct net_device *) data;
> - struct inet6_dev *idev;
> + struct inet6_dev *idev = __in6_dev_get(dev);
> int run_pending = 0;
> int err;
>
> - if (event == NETDEV_UNREGISTER_FINAL)
> - return NOTIFY_DONE;
> -
> - idev = __in6_dev_get(dev);
> switch (event) {
> case NETDEV_REGISTER:
> if (!idev && dev->mtu >= IPV6_MIN_MTU) {
--
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