In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: remove one synchronize_net() barrier in ipv6_mc_down() As discussed in the past (commit 2d3916f31891 ("ipv6: fix skb drops in igmp6_event_query() and igmp6_event_report()")) I think the synchronize_net() call in ipv6_mc_down() is not needed. Under load, synchronize_net() can last between 200 usec and 5 ms. KASAN seems to agree as well.
https://git.kernel.org/stable/c/a03ede2282ebbd181bd6f5c38cbfcb5765afcd04
https://git.kernel.org/stable/c/9d159d6637ccce25f879d662a480541ef4ba3a50
https://git.kernel.org/stable/c/7eb06ee5921189812e6b4bfe7b0f1e878be16df7
https://git.kernel.org/stable/c/5da9a218340a2bc804dc4327e5804392e24a0b88
https://git.kernel.org/stable/c/26d4bac55750d535f1f0b8790dc26daf6089e373
https://git.kernel.org/stable/c/17ef8efc00b34918b966388b2af0993811895a8c