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ipv6: avoid unregistering inet6_dev for loopback

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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 176c39af29
("netns: fix addrconf_ifdown kernel panic") we always
override the case for loopback.

Thanks a lot to Andrey for finding a reliable reproducer.

Fixes: 176c39af29 ("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>
This commit is contained in:
WANG Cong 2017-06-21 14:34:58 -07:00 committed by David S. Miller
parent 8c4354ef59
commit 60abc0be96
1 changed files with 3 additions and 2 deletions
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5
net/ipv6/addrconf.c
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@ -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;