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Commit 60abc0be authored by WANG Cong's avatar WANG Cong Committed by David S. Miller
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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: default avatarAndrey 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: default avatarCong Wang <xiyou.wangcong@gmail.com>
Acked-by: default avatarDavid Ahern <dsahern@gmail.com>
Tested-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Signed-off-by: default avatarDavid 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;