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mm/hugetlb: fix missing hugetlb_lock for resv uncharge

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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: 79aa925bf2 ("hugetlb_cgroup: fix reservation accounting")
Signed-off-by: Peter Xu <peterx@redhat.com>
Reported-by: syzbot+4b8077a5fccc61c385a1@syzkaller.appspotmail.com
Reviewed-by: Mina Almasry <almasrymina@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Peter Xu 2024-04-17 17:18:35 -04:00 committed by Andrew Morton
parent 6db7412c14
commit b76b46902c
1 changed files with 4 additions and 1 deletions
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5
mm/hugetlb.c
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@ -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)