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 <davem@davemloft.net>
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 34ccef1..4c87594 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -6996,7 +6996,7 @@
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 @@
*/
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 @@
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 a63ff85..7421207 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -155,10 +155,9 @@
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 @@
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 @@
{
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);
}
}
