6.8-stable review patch. If anyone has any objections, please let me know.
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From: Peter Xu peterx@redhat.com
commit b76b46902c2d0395488c8412e1116c2486cdfcb2 upstream.
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: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/hugetlb.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3266,9 +3266,12 @@ 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); + } }
if (!memcg_charge_ret)