[PATCH 6.1 017/236] mm/hugetlb: fix missing hugetlb_lock for resv uncharge

Greg Kroah-Hartman
2024-05-14T11:29:36Z

From: Peter Xu <peterx@redhat.com>

[ Upstream commit b76b46902c2d0395488c8412e1116c2486cdfcb2 ]

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: 79aa925bf239 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
mm/hugetlb.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e720b9ac28337..e9ae0fc81dfbe 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3190,9 +3190,12 @@ struct page *alloc_huge_page(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);
+ }
}
return page;

--
2.43.0