ipv6: blackhole_netdev needs snmp6 counters

net-next inclusion
from net-next-v5.17-rc5
commit dd263a8c
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4VZN0?from=project-issue

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=dd263a8cb1941d2d34a55633bd5366d9bebf4be8



--------------------------------

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>
Conflicts:
	net/ipv6/addrconf.c
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Reviewed-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>