Commit b76b4690 authored by Peter Xu's avatar Peter Xu Committed by Andrew Morton
Browse files

mm/hugetlb: fix missing hugetlb_lock for resv uncharge 

There is a recent report on UFFDIO_COPY over hugetlb:

https://lore.kernel.org/all/000000000000ee06de0616177560@google.com/

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.

Link: https://lkml.kernel.org/r/20240417211836.2742593-3-peterx@redhat.com


Fixes: 79aa925b ("hugetlb_cgroup: fix reservation accounting")
Signed-off-by: default avatarPeter Xu <peterx@redhat.com>
Reported-by: default avatar <syzbot+4b8077a5fccc61c385a1@syzkaller.appspotmail.com>
Reviewed-by: default avatarMina Almasry <almasrymina@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 6db7412c

mm/hugetlb.c

+4 −1
Original line number Diff line number Diff line
@@ -3268,9 +3268,12 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, 


		rsv_adjust = hugepage_subpool_put_pages(spool, 1);

		hugetlb_acct_memory(h, -rsv_adjust);

		if (deferred_reserve)

		if (deferred_reserve) {

			spin_lock_irq(&hugetlb_lock);

			hugetlb_cgroup_uncharge_folio_rsvd(hstate_index(h),

					pages_per_huge_page(h), folio);

			spin_unlock_irq(&hugetlb_lock);

		}

	}



	if (!memcg_charge_ret)