CVE-2024-27390

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.