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 6.6-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-uncharge.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b76b46902c2d0395488c8412e1116c2486cdfcb2 Mon Sep 17 00:00:00 2001
From: Peter Xu <peterx@xxxxxxxxxx>
Date: Wed, 17 Apr 2024 17:18:35 -0400
Subject: mm/hugetlb: fix missing hugetlb_lock for resv uncharge
From: Peter Xu <peterx@xxxxxxxxxx>
commit b76b46902c2d0395488c8412e1116c2486cdfcb2 upstream.
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: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3153,9 +3153,12 @@ struct folio *alloc_hugetlb_folio(struct
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 folio;
Patches currently in stable-queue which might be from peterx@xxxxxxxxxx are
queue-6.6/mm-hugetlb-fix-missing-hugetlb_lock-for-resv-uncharge.patch
