published May 20, 2024
In the Linux kernel, the following vulnerability has been resolved:
mm/hugetlb: fix missing hugetlb_lock for resv uncharge
There is a recent report on UFFDIO_COPY over hugetlb:
https://lore.kernel.org/all/[email protected]/
350: lockdep_assert_held(&hugetlb_lock);
Should be an issue in hugetlb but triggered in an userfault context, where
it goes into the unlikely path where two threads modifying the resv map
together. Mike has a fix in that path for resv uncharge but it looks like
the locking criteria was overlooked: hugetlb_cgroup_uncharge_folio_rsvd()
will update the cgroup pointer, so it requires to be called with the lock
held.