CVE-2026-63981 net/sched: act_mirred: Fix blockcast recursion bypass leading to stack overflow

In the Linux kernel, the following vulnerability has been resolved: net/sched: actmirred: Fix blockcast recursion bypass leading to stack overflow tcfmirredact checks schedmirrednest against MIRREDNESTLIMIT 4 to prevent deep recursion. However, when the action uses blockcast tcfmblockid != 0, the...