From b0818f80c8c1bc215bba276bd61c216014fab23b Mon Sep 17 00:00:00 2001 From: Mahesh Bandewar Date: Fri, 11 Oct 2019 18:14:55 -0700 Subject: blackhole_netdev: fix syzkaller reported issue While invalidating the dst, we assign backhole_netdev instead of loopback device. However, this device does not have idev pointer and hence no ip6_ptr even if IPv6 is enabled. Possibly this has triggered the syzbot reported crash. The syzbot report does not have reproducer, however, this is the only device that doesn't have matching idev created. Crash instruction is : static inline bool ip6_ignore_linkdown(const struct net_device *dev) { const struct inet6_dev *idev = __in6_dev_get(dev); return !!idev->cnf.ignore_routes_with_linkdown; <= crash } Also ipv6 always assumes presence of idev and never checks for it being NULL (as does the above referenced code). So adding a idev for the blackhole_netdev to avoid this class of crashes in the future. Signed-off-by: David S. Miller --- net/ipv6/addrconf.c | 7 ++++++- net/ipv6/route.c | 15 ++++++--------- 2 files changed, 12 insertions(+), 10 deletions(-) (limited to 'net/ipv6') diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 34ccef18b40e..4c87594d1389 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -6996,7 +6996,7 @@ static struct rtnl_af_ops inet6_ops __read_mostly = { int __init addrconf_init(void) { - struct inet6_dev *idev; + struct inet6_dev *idev, *bdev; int i, err; err = ipv6_addr_label_init(); @@ -7036,10 +7036,14 @@ int __init addrconf_init(void) */ rtnl_lock(); idev = ipv6_add_dev(init_net.loopback_dev); + bdev = ipv6_add_dev(blackhole_netdev); rtnl_unlock(); if (IS_ERR(idev)) { err = PTR_ERR(idev); goto errlo; + } else if (IS_ERR(bdev)) { + err = PTR_ERR(bdev); + goto errlo; } ip6_route_init_special_entries(); @@ -7124,6 +7128,7 @@ void addrconf_cleanup(void) addrconf_ifdown(dev, 1); } addrconf_ifdown(init_net.loopback_dev, 2); + addrconf_ifdown(blackhole_netdev, 2); /* * Check hash table. diff --git a/net/ipv6/route.c b/net/ipv6/route.c index a63ff85fe141..742120728869 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -155,10 +155,9 @@ void rt6_uncached_list_del(struct rt6_info *rt) static void rt6_uncached_list_flush_dev(struct net *net, struct net_device *dev) { - struct net_device *loopback_dev = net->loopback_dev; int cpu; - if (dev == loopback_dev) + if (dev == net->loopback_dev) return; for_each_possible_cpu(cpu) { @@ -171,7 +170,7 @@ static void rt6_uncached_list_flush_dev(struct net *net, struct net_device *dev) struct net_device *rt_dev = rt->dst.dev; if (rt_idev->dev == dev) { - rt->rt6i_idev = in6_dev_get(loopback_dev); + rt->rt6i_idev = in6_dev_get(blackhole_netdev); in6_dev_put(rt_idev); } @@ -386,13 +385,11 @@ static void ip6_dst_ifdown(struct dst_entry *dst, struct net_device *dev, { struct rt6_info *rt = (struct rt6_info *)dst; struct inet6_dev *idev = rt->rt6i_idev; - struct net_device *loopback_dev = - dev_net(dev)->loopback_dev; - if (idev && idev->dev != loopback_dev) { - struct inet6_dev *loopback_idev = in6_dev_get(loopback_dev); - if (loopback_idev) { - rt->rt6i_idev = loopback_idev; + if (idev && idev->dev != dev_net(dev)->loopback_dev) { + struct inet6_dev *ibdev = in6_dev_get(blackhole_netdev); + if (ibdev) { + rt->rt6i_idev = ibdev; in6_dev_put(idev); } } -- cgit v1.2.3-59-g8ed1b