This is a note to let you know that I've just added the patch titled
mm/hugetlb: fix missing hugetlb_lock for resv uncharge
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-hugetlb-fix-missing-hugetlb_lock-for-resv-uncharg.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 96a4292507e27a400170d094e88ec31997277544
Author: Peter Xu <peterx@xxxxxxxxxx>
Date: Wed Apr 17 17:18:35 2024 -0400
mm/hugetlb: fix missing hugetlb_lock for resv uncharge
[ Upstream commit b76b46902c2d0395488c8412e1116c2486cdfcb2 ]
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.
Link: https://lkml.kernel.org/r/20240417211836.2742593-3-peterx@xxxxxxxxxx
Fixes: 79aa925bf239 ("hugetlb_cgroup: fix reservation accounting")
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Reported-by: syzbot+4b8077a5fccc61c385a1@xxxxxxxxxxxxxxxxxxxxxxxxx
Reviewed-by: Mina Almasry <almasrymina@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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;
