CVE-2022-49589

In the Linux kernel, the following vulnerability has been resolved:

igmp: Fix data-races around sysctligmpqrv.

While reading sysctligmpqrv, 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.

qrv ?: READONCE(net->ipv4.sysctligmp_qrv);