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

mm/damon/vaddr: do not repeat pte_offset_map_lock() until success

DAMON's virtual address space operation set implementation (vaddr) calls
pte_offset_map_lock() inside the page table walk callback function.  This
is for reading and writing page table accessed bits.  If
pte_offset_map_lock() fails, it retries by returning the page table walk
callback function with ACTION_AGAIN.

pte_offset_map_lock() can continuously fail if the target is a pmd
migration entry, though.  Hence it could cause an infinite page table walk
if the migration cannot be done until the page table walk is finished. 
This indeed caused a soft lockup when CPU hotplugging and DAMON were
running in parallel.

Avoid the infinite loop by simply not retrying the page table walk.  DAMON
is promising only a best-effort accuracy, so missing access to such pages
is no problem.