On Wed, Apr 17, 2024 at 2:18 PM Peter Xu <peterx@xxxxxxxxxx> wrote: > > There is a recent report on UFFDIO_COPY over hugetlb: > > https://lore.kernel.org/all/000000000000ee06de0616177560@xxxxxxxxxx/ > > 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. > > Looks like a stable material, so have it copied. > > Reported-by: syzbot+4b8077a5fccc61c385a1@xxxxxxxxxxxxxxxxxxxxxxxxx > Cc: Mina Almasry <almasrymina@xxxxxxxxxx> > Cc: David Hildenbrand <david@xxxxxxxxxx> > Cc: linux-stable <stable@xxxxxxxxxxxxxxx> > Fixes: 79aa925bf239 ("hugetlb_cgroup: fix reservation accounting") > Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> Reviewed-by: Mina Almasry <almasrymina@xxxxxxxxxx> > --- > mm/hugetlb.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 26ab9dfc7d63..3158a55ce567 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -3247,9 +3247,12 @@ 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) > -- > 2.44.0 > -- Thanks, Mina
