Commit dd263a8c authored Feb 13, 2022 by Ido Schimmel Committed by David S. Miller Feb 14, 2022

ipv6: blackhole_netdev needs snmp6 counters



Whenever rt6_uncached_list_flush_dev() swaps rt->rt6_idev
to the blackhole device, parts of IPv6 stack might still need
to increment one SNMP counter.

Root cause, patch from Ido, changelog from Eric :)

This bug suggests that we need to audit rt->rt6_idev usages
and make sure they are properly using RCU protection.

Fixes: e5f80fcf ("ipv6: give an IPv6 dev to blackhole_netdev")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 7db45f8d

net/ipv6/addrconf.c

+9 −9

Original line number	Diff line number	Diff line
		@@ -400,7 +400,6 @@ static struct inet6_dev ipv6_add_dev(struct net_device dev)
		/* We refer to the device */
		dev_hold_track(dev, &ndev->dev_tracker, GFP_KERNEL);

		if (dev != blackhole_netdev) {
		if (snmp6_alloc_dev(ndev) < 0) {
		netdev_dbg(dev, "%s: cannot allocate memory for statistics\n",
		__func__);
		@@ -410,6 +409,7 @@ static struct inet6_dev ipv6_add_dev(struct net_device dev)
		return ERR_PTR(err);
		}

		if (dev != blackhole_netdev) {
		if (snmp6_register_dev(ndev) < 0) {
		netdev_dbg(dev, "%s: cannot create /proc/net/dev_snmp6/%s\n",
		__func__, dev->name);