Commit 60abc0be authored Jun 21, 2017 by WANG Cong Committed by David S. Miller Jun 22, 2017

ipv6: avoid unregistering inet6_dev for loopback



The per netns loopback_dev->ip6_ptr is unregistered and set to
NULL when its mtu is set to smaller than IPV6_MIN_MTU, this
leads to that we could set rt->rt6i_idev NULL after a
rt6_uncached_list_flush_dev() and then crash after another
call.

In this case we should just bring its inet6_dev down, rather
than unregistering it, at least prior to commit 176c39af
("netns: fix addrconf_ifdown kernel panic") we always
override the case for loopback.

Thanks a lot to Andrey for finding a reliable reproducer.

Fixes: 176c39af ("netns: fix addrconf_ifdown kernel panic")
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Daniel Lezcano <dlezcano@fr.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: David Ahern <dsahern@gmail.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 8c4354ef

net/ipv6/addrconf.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -3369,6 +3369,7 @@ static int addrconf_notify(struct notifier_block *this, unsigned long event,
		struct net_device *dev = netdev_notifier_info_to_dev(ptr);
		struct netdev_notifier_changeupper_info *info;
		struct inet6_dev *idev = __in6_dev_get(dev);
		struct net *net = dev_net(dev);
		int run_pending = 0;
		int err;

		@@ -3384,7 +3385,7 @@ static int addrconf_notify(struct notifier_block *this, unsigned long event,
		case NETDEV_CHANGEMTU:
		/* if MTU under IPV6_MIN_MTU stop IPv6 on this interface. */
		if (dev->mtu < IPV6_MIN_MTU) {
		addrconf_ifdown(dev, 1);
		addrconf_ifdown(dev, dev != net->loopback_dev);
		break;
		}

		@@ -3500,7 +3501,7 @@ static int addrconf_notify(struct notifier_block *this, unsigned long event,
		* IPV6_MIN_MTU stop IPv6 on this interface.
		*/
		if (dev->mtu < IPV6_MIN_MTU)
		addrconf_ifdown(dev, 1);
		addrconf_ifdown(dev, dev != net->loopback_dev);
		}
		break;

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