CVE-2021-47567

In the Linux kernel, the following vulnerability has been resolved:
powerpc/32: Fix hardlockup on vmap stack overflow Since the commit
c118c7303ad5 (“powerpc/32: Fix vmap stack - Do not activate MMU before
reading task struct”) a vmap stack overflow results in a hard lockup. This
is because emergency_ctx is still addressed with its virtual address
allthough data MMU is not active anymore at that time. Fix it by using a
physical address instead.