igmp: Fix data-races around sysctl_igmp_llm_reports.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2149949


Upstream Status: linux.git

commit f6da2267
Author: Kuniyuki Iwashima <kuniyu@amazon.com>
Date:   Fri Jul 15 10:17:41 2022 -0700

    igmp: Fix data-races around sysctl_igmp_llm_reports.

    While reading sysctl_igmp_llm_reports, it can be changed concurrently.
    Thus, we need to add READ_ONCE() to its readers.

    This test can be packed into a helper, so such changes will be in the
    follow-up series after net is merged into net-next.

      if (ipv4_is_local_multicast(pmc->multiaddr) &&
          !READ_ONCE(net->ipv4.sysctl_igmp_llm_reports))

    Fixes: df2cf4a7 ("IGMP: Inhibit reports for local multicast groups")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Guillaume Nault <gnault@redhat.com>